(CNN) A Wisconsin girl whose friends lured her into the woods after a slumber party and stabbed her 19 times to impress a fictional horror character is sharing her story.

Payton Leutner was stabbed by two 12-year-old classmates at a Waukesha park in 2014. The attack by Morgan Geyser and Anissa Weier stunned the nation -- especially after it emerged that they targeted her due to their fixation on "Slender Man," an internet boogeyman

In a deal with prosecutors, Geyser pleaded guilty to attempted first-degree murder and got 40 years in a mental institution instead of serving jail time. Weier pleaded guilty to attempted second-degree homicide due to mental illness and a judge sentenced her to 25 years in a mental health facility

In an exclusive interview with ABC's "20/20" set to air Friday, Leutner, who's now 17, said the attack traumatized her physically and emotionally, and she sleeps with a pair of broken scissors. She said she finds it hard to make new friends because she cannot trust people easily.

"She has friends, but initially, even with those friends, she kept them at arm's length," her mother, Stacie Leutner, told ABC. "And for a long time, even trusting family members was hard for her."

CNN does not typically name minors charged with crimes, but makes exceptions if they are charged as an adult, as were Geyser and Weier.

The night before the attack

In May 2014, the trio had gone to Geyser's home for a slumber party to celebrate her birthday.

It was a regular day for them -- they'd previously spent a lot of time together playing outside, drawing and having sleepovers, Leutner said. During those times, Geyser constantly talked about Slender Man, a character that terrified Leutner, she said.

So much so, Leutner asked her mother if Slender Man was real and she reassured her that he was not. Slender Man -- a menacing, faceless specter in a dark suit, sometimes portrayed with octopus-like tentacles -- is said to haunt children and lurks in the darkest corners of the Web. The internet monster was created in an online forum for people who enjoy creating fake supernatural images.

"I thought it was odd. It kind of frightened me a little bit," Leutner told ABC of her friends' fascination with the character. "But I went along with it. I was supportive because I thought that's what she liked."

As the friendship between Geyser and Weier grew, so did the pair's fixation with Slender Man, Leutner said.

The birthday party

While she didn't know her friend planned to harm her after they celebrated Geyser's 12th birthday at a local roller rink followed by a slumber party, something felt off that night in retrospect, she said.

"At all of our past sleepovers, [Geyser] always wanted to stay up all night because she could never do that at home," Leutner said. "But on [the night of] the birthday party, she wanted to go to bed."

Her friends later told investigators that they had planned to kill Leutner in her sleep that night but then decided to do it the next morning at a nearby park.

When she woke up, they were downstairs on the computer so she joined them for doughnuts before heading to the park. While there, they told her the plan was to play hide-and-seek and asked her to lie down under the leaves and sticks as part of the game, she said.

"But it was really just a trick to get me down there," she said.

That's when Geyser repeatedly stabbed her with a kitchen knife and the girls left her alone in the woods, bleeding and struggling get help.

After she crawled out of the woods, a passing bicyclist found her and called 911.