Atlanta (CNN) It's been about four years since Aimee Copeland lost her hands, a leg and a foot in a fight with flesh-eating bacteria, and she is bragging about beating friends in arm wrestling.

She's sitting on a mat in a small exercise room of her Atlanta house, with ankle weights slipped over her surgically shortened arms, wearing no prosthetic save for the right foot she uses to help her slide and twist off her wheelchair.

She lifts her arms and lowers them, demonstrating one of the many exercises she does for near-daily 90-minute sessions.

A fight with flesh-eating bacteria four years ago left Aimee Copeland without her left leg, her right foot and both hands.

"Arm strength is so important when you're missing one whole leg," she says, before musing about how strong she is. "I've beaten pretty much everybody at this house in arm wrestling," she explains, without even using her hand prostheses. Her opponents grabbed the end of her arm, elbows on the table, and she took them down.

Her housemate Esther hears her from another room and laughs.

"You are evil," Esther says.

"One was a guy," Copeland offers.

"I was going to say," Esther laughs.

Copeland, 28, has long been active and outdoorsy. Before her accident, she hiked parts of the Appalachian Trail, rode her bike to class, went rock climbing in Alabama and dabbled in whitewater kayaking.

Copeland, seen in April with her service dog, Belle, moved from her parents' home to her Atlanta house last year.

Strength training and this room, for now, make up a large portion of the workout pie. They counter hours of sitting -- she relies largely on a motorized wheelchair to get around since an infection left her without much of her four limbs and thrust her into a national spotlight as she clung to life.

But she also wants to be strong in case she's eventually able to have an operation on one of her thigh bones -- the one amputated nearly to the hip -- to let her walk well with prostheses for the first time since her accident. Right now, it's generally too impractical to walk, let alone hike, beyond what she does on a treadmill.

"I do want to walk -- that's my No. 1 goal," she says, and exercising will help make sure she's ready.

It's been one hell of a journey: she's left her parents' care, finished two master's degrees, got a new boyfriend, is about to start a new job, and has ambitious plans to serve others through a nonprofit she hopes to create one day. It's a path that she found after a lot of pain, screaming and dark nights.

And it's a trek that happened only because of a zip line ride that she didn't even plan on taking.

The accident

It's May 1, 2012, and Aimee Copeland ends her waitressing shift at a café with no particular plans for the afternoon.

She'd finished classes for the semester at the University of West Georgia in Carrollton, working on her first master's degree in psychology. A friend calls, and she's having a hard time, so Copeland goes to her pal's rented home in town to hang out.

Before the accident, Copeland was an outdoors-loving graduate student.

They and another friend go to the backyard and check out a garden and some rabbits living in a shed. It's warm, in the 80s, and a creek in the back of the property beckons, so they go put on their bathing suits.

It's only as they wade into the creek that they notice a dog runner cable with handlebars, extending over the water about 6 feet across and 6 feet high on a neighbor's property.

They take a few turns on the zip line. On Copeland's second run, she hears something.

Snap!

The line breaks and she falls into the creek, feeling a stabbing pain in her left leg. Sharp rocks have gashed her calf, and she's bleeding.

Copeland, left, is shown before her accident with her mother, Donna, her father, Andy, and her sister, Paige.

She needs 22 staples at a local hospital to close the wound. Over the next two days, she twice goes to doctors complaining of severe pain, and gets painkillers, antibiotics and an MRI.

On May 4 she wakes up to see her left leg rotting, purple to the hip. She can't walk, her tongue is shriveled, and it's all she can do to manage a few words to her boyfriend.

"I think I'm dying," she says. He picks her up and rushes her back to the hospital, where she's diagnosed with necrotizing fasciitis, a bacterial infection that is destroying her tissue.

A heart attack 'simply being moved from the stretcher'

She'd contracted Aeromonas hydrophila, which more commonly causes diarrhea in swimmers who swallow contaminated water, but is one of several types of bacteria that can, rarely, cause necrotizing fasciitis should it enter an open wound.

If treated early enough, a patient might only need skin or fat removal. Some patients need amputations. It's hard to tell how many American patients get the disease yearly. The Centers for Disease Control and Prevention says it tracks necrotizing fasciitis only from the most common bacterial cause -- strep -- and that results in about 700 to 1,100 cases of infection every year in the US.

Copeland was released from a hospital on July 2, 2012. She spent weeks at an Atlanta rehabilitation center before going home.

Up to 25% of patients die because of complications such as organ failure and blood poisoning, the National Institutes of Health says.

Copeland, her leg too far gone, nearly fell in that last group.

She was flown to a hospital in Augusta, where doctors amputated her left leg and cut skin from her abdomen to stop the bacteria's spread.

"All my vital organs were also failing," she recalled in her interview with CNN this year. "I coded simply being moved from the stretcher to table and had to be resuscitated."

A respirator breathed for her, and she was on full-time dialysis. Three days after her amputation, a doctor told her parents that her chances of survival were slim to none.

News outlets across the country followed the story, captivated by her youth, the zip line accident and her struggle to stay alive.

'The first thing that I remember'

The short way to explain Copeland's four amputations is to say they happened because of flesh-eating bacteria. That's correct only to a point.

Doctors amputated her left leg because of bacteria, but the disease didn't damage her hands and right foot. The medicine used to save her life did that, her family says.

She was put on vasopressors, drugs that tighten blood vessels and raise blood pressure. For days, they ensured blood flow to her vital organs but eventually starved her extremities.

By May 17, 2012, her remaining limbs had paid the price.

"The first thing that I remember coherently is my father holding up my hands for me to see," she recalls. "My hands were curled up. They were dark purple in the palms, black at the fingertips. And my dad said, 'You know, these aren't healthy. We're going to have to remove your hands. They could threaten your life.'

"That was the point where I consciously chose to fight for life."

Her father, Andy, recorded his daughter's words that day in a blog: "Let's do this," she said, agreeing to the amputations.

He cried as he left the room, he wrote, because "in all my 53 years of existence, I have never seen such a strong display of courage."

Recipe for recovery

Four years on, long after her rehab ended and the near-daily requests for media interviews dried up, Copeland reflects in her Atlanta house in April about how she's changed. It's an appropriate time to mention Babe the pig.

Copeland was a vegetarian before her accident, first shunning pork after seeing the movie "Babe" as a kid, then going all-veggie in college after seeing "Food, Inc." But that wasn't tenable as a quadruple amputee.

She uses myoelectric hand prostheses for finer movements, like when she's preparing food. "One big reason I wanted to move out of my parents' house was to get my own kitchen," she says. "I love to cook."

After having skin grafts to close her hip and abdomen, hundreds of crunches and leg lifts daily helped her develop the core she needed for simple things like transferring herself from a bed to a wheelchair.

For that, she needed protein. Meat seemed a crucial part of the solution.

Sorry, Babe. If she has regrets, she hides it well.

"I've just gone full meat, and it's amazing," she says. "I've been missing out on bacon all these years."

Fitness is like a job, in part for practicality. Sedentary in the hospital, she left in July 2012 weighing 120 pounds, almost as much as she weighed when she came in, despite losing 30 pounds in limbs.

She's down to 98 pounds now, doing something in the workout room -- arms, legs, abs, treadmill -- for 90 minutes daily. Less weight means less struggle for transfers, or for friends who need to lift her and her wheelchair up steps to someone's ramp-less home.

Exercise in this room is a daily routine.

Home is the place where she really had to come to terms with a new life. By August 2012, after months of painful rehab, she was back at her parents' Snellville house, east of Atlanta. A homebuilder donated a renovation to the home, with ramps, more space and other features to meet her needs.

She'd be fit with a series of progressively advanced prostheses. Fit initially with hooks for hands, she learned how to pick up a pair of shorts and put them on, her father told reporters.

She hadn't lived with her parents for six years, and her college friends and boyfriend lived far away. He ultimately didn't handle the situation well, as she puts it, and they eventually broke up. "Losing someone that I was that close to, I would say, was more difficult than the limb loss itself," she says.

She uses the ends of her arms for many everyday tasks, like typing on her iPad. Here, she works at her internship at Atlanta's Shepherd Center in April.

She'd scream and cry at night, full of questions. Would she walk again? Could she live independently? Would she ever date again? Anxiety gripped her for two years.

Gradually she accepted the situation and developed a new life plan. Family and faith, she says, were key.

"My dad would always tell me that you can either have faith or you can have fear in those moments," says Copeland, who grew up in a Baptist home and says she now draws on many spiritual traditions. "He is one of those people that really kept me going and just made me believe that everything would work out in the end."

"I think it's my job not to judge things as good or bad or think that I'm the all-knowing of how things should be. ... If anything, I think these are the tests, poking and prodding, to determine, do you really have faith, or are you just happy with your circumstances right now? In the worst possible circumstances, can you still have faith?"

'He told me ... my body is perfect'

Years after those dark nights, she figures life is looking sweet, including on the job and romance fronts.

At West Georgia, the psychology graduate student was examining eco-therapy -- how to help people using nature and the outdoors. She wasn't sure who she wanted to work with. Troubled teens? Alcoholics?

Her accident gave her the answer.

"The more I laid in that hospital bed day after day, saw other people laying in their hospital beds day after day watching soap operas and daytime TV, the more I realized, 'Wow, this population is actually in most need of ecopsychology than any other population I've ever worked with,'" she says.

Copeland talks in April to the wife of a patient at Atlanta's Shepherd Center, where she underwent rehab herself four years ago. This year she was a social work intern at the hospital, which treats people with spinal cord, brain and other traumatic injuries.

The plan now -- years down the line -- is to start a non-profit center where she would counsel people, especially those who've faced traumatic, life-threatening injuries. It would include a large park setting for things like camping and hiking.

"There's nowhere I could just go and ... be a therapist with that population using the modalities -- exercise, nutrition, gardening, personal training, yoga -- that I want," she says.

She'd need to raise funds; she already has a business plan. But before that she needs experience. After finishing her West Georgia master's, she earned a master's in social work online through Valdosta State in May.

She'll start working at a mental health clinic in November -- a confidentiality agreement keeps her from naming the facility -- as a licensed master social worker. After 3,000 hours of direct practice, she could pass another exam and become a licensed clinical social worker, which would allow her to practice without supervision.

Copeland moved into her own house with her friend Esther in Atlanta last year, and renovated it -- what was once a bathroom uncomfortably small for her wheelchair, for example, is now a closet.

She used the house as her base as she finished her second master's, typing papers on her trusty iPad with the ends of her arms. Swiping and pressing with her arms is much faster than using prostheses, she says.

Copeland reclines this year at a beach during a family vacation in San Juan, Puerto Rico. "It has taken me a long time to become comfortable with and accept my new body," she wrote when posting this picture to Facebook in June. "We are ALL made with imperfections and there is so much beauty in our flaws. The scars and skin grafting build character! It's not about what you have -- what you do with what you have is what really counts."

She sometimes slips on myoelectric prosthetic hands that respond to electric signals from her arm muscles. They're for when she needs finer movements, like for grooming and cooking. The fingers respond with various programmed grips, and she cycles through them with a gesture.

They aren't on her all the time -- she likens them to footwear. "Even the most comfortable shoes, you want to take them off at the end of the day."

As for romance: After all her doubt, a friend talked her into online dating last year.

"I had to go through, you know, quite a few people, talking (to) and getting to know different people," she says. "And that's when I met my current boyfriend."

That would be Stephen, a high school English teacher who, it turned out, had attended West Georgia for his undergraduate degree. They had mutual friends.

"I immediately went to them and got the dirt, and he checked out."

Copeland in her Atlanta house. "My life has been (shaped) by everything that happened to me."

He had heard her story before they met. When they did, it clicked.

"He told me that he thinks my body is perfect. So to me, that's just what I want to hear -- that somebody can accept me despite all that I've been through, and he's amazing."

They've been together for more than a year.

'I would go on that zip line again'

She thinks there isn't much that can rattle her anymore. In August 2015, someone stole her adapted van, donated by a dealership, in front of her home. She reported the theft and fired up her iPad to see how she was going to get to her social work internship at an Atlanta hospital the next day at 7:30 a.m.

Two buses and a train might do the trick, but what if she missed one? This was her third day on the job; no time to look unreliable. She mapped it out -- 5 miles by sidewalk.

So out she rolled at dawn in the wheelchair, scooting at 5 mph alongside Atlanta's busy roadways, from her near-downtown neighborhood and over an interstate to her job.

"Several people were like, 'Why didn't you call me?'" she recalls.

She shrugs it off. That van was found, left in good shape by whoever stole it.

"At this point, I can pretty much take anything. There's no news that could match up with, 'We're taking all your limbs off.'"

Copeland looks forward to her career of service. She says she's in the best shape of her life, and the happiest she's ever been.

She says she'd even go on that zip line again if she could do it over.

"Knowing the impact that I have and will continue to have, and knowing how this experience has shaped my life for the better, a million and one times, I would go on that zip line again," she recently told students and faculty at West Georgia.

Of course she'd like her legs and hands back, she adds later. But "my life has been (shaped) by everything that happened to me," she says. "I wouldn't trade everything that I gained to get them back."

She's good with life, but not happy with her mobility. The real game-changer would be walking.

Learning to walk again

Only 2 inches of her left femur remain. That means her prosthetic must be fit as if she's missing three joints -- ankle, knee and hip -- and that makes standing and walking very difficult. It also leads to debilitating skin sores at her graft site.

Walking now is so difficult, it's largely relegated to the treadmill. She hopes a surgery will one day let her walk more easily.

What might help, she says, is a procedure called osseointegration, in which a surgeon would attach a metal plate to what remains of her left femur, and let the bone fuse with the metal. The plate would have a port, which could be inserted into a prosthetic. That more stable attachment between body and prosthetic could help her walk better.

That could take time -- the procedure is not FDA approved, though she says she hopes she could be a test subject one day.

She can't wait. She misses easy access to, well, everything.

Join the conversation See the latest news and share your comments with CNN Health on Facebook and Twitter.

"If I want to go to my friends' house independently and not have to be lifted in, if I want to hike and backpack again, then (surgery) will be necessary."

Back in her exercise room, she demonstrates just how hard walking is. Wearing her left leg and right foot prostheses, she rises from her wheelchair with Esther's help and steps onto a treadmill. Leaning on an armrest, she swings her left leg around, followed by a step with the right, about a step per second. At one point, her right foot gets caught while going forward. She almost falls, but leans into the armrest to catch herself.

"Don't be alarmed," she laughs nervously. "I have fallen many times."

And gotten back up.