 -- Michelle Carter, who as a teenager sent texts urging her then-boyfriend to commit suicide, was sentenced today to 2.5 years in the Bristol County House of Correction for involuntary manslaughter, with 15 months to be served and the rest suspended, followed by five years of probation.

In announcing Carter's sentencing, Judge Lawrence Moniz said that she could stay free pending appeals.

Conrad Roy III was 18 when he died in July 2014 of carbon monoxide poisoning after locking himself in his truck in Massachusetts.

Carter, now 20, who was Roy's girlfriend at the time of his death, went on trial this year, and the prosecution argued that Carter, then 17, was reckless and caused his death by telling Roy to get back in the car even though they say he didn’t want to die.

"I could’ve stopped him," Carter texted a classmate two months after Roy's death, according to testimony. Carter texted that she and Roy were on the phone the day of his suicide when Roy "got out of the car ... he was scared." Carter texted that she "told him to get back in."

The defense claimed that Carter had previously tried to talk Roy out of harming himself, pointing to one conversation where Roy told Carter he regretted dragging her into his plans to kill himself.

Earlier today, the prosecution asked Moniz to sentence Carter to seven to 12 years in prison.

"She ended his life to better her own," the prosecution said, adding that Carter has not accepted responsibility for her actions.

Meanwhile, earlier today the defense asked for five years of supervised probation with conditions including mental health treatment and no contact with the Roy family. Her defense attorney added that Carter regrets what happened and stressed that the sentence should be rehabilitative, not punitive.

Conrad Roy's sister, Camden Roy, gave a statement in court today ahead of the sentencing, calling her brother the best friend and role model "any little sister could ask for."

Conrad Roy's father, Conrad Roy Jr., said in court before sentencing, "I cannot being to describe the despair I feel over the loss of my son. ... I am heartbroken, our family is heartbroken. My son was my best friend."

He called his son sensitive, loving, compassionate and an excellent older brother who was "adored" by his sisters.

"How could Michelle Carter behave so viciously?" he said. "Where was her humanity?"

He said the last words he said to his son were "I love you."

"I miss him every moment of every day," Conrad Roy Jr. said.

Lynn Roy, Conrad Roy's mother, said in court before sentencing, "I still cannot come to terms that another person who knew and described how much they loved my son would want to inflict so much pain" on Conrad Roy's family. "He is the most amazing human being and would have had a bright future.

"This does not stop after a trial. I pray that his death will save lives some day," she added.

In June, Moniz found Carter guilty of involuntary manslaughter, describing her behavior as "reckless." Involuntary manslaughter is defined as an unintentional killing resulting from recklessness or criminal negligence.

While announcing the verdict, Moniz said that Carter instructed Conrad Roy "to get back into the truck well knowing of all of the feelings he [had] exchanged with her, his ambiguities, his fears, his concerns."

"This court finds that instructing Mr. Roy to get back in the truck constituted wanton and reckless conduct," Moniz said.

The judge also noted that Carter admitted in texts that she took no action; she knew the location of the truck and did not notify Conrad Roy's mother or sisters.

Carter was charged as a youthful offender, which means that even though she was a minor at the time of the incident, she was charged as an adult. The maximum possible sentence was 20 years.

Conrad Roy's aunt Kim Bozzi told ABC News' "20/20" ahead of the sentencing, "I don't think that she helped him kill himself. ... I think she forced him to kill himself. I think she was responsible for his death."

Kim Bozzi said when she read the text about Carter telling Conrad Roy to get back in the truck, "My heart broke because, unfortunately, he did."

Bozzi said the most "unbelievable" part of Carter's actions was "how she acted after the fact. She was there, sitting on the phone, talking to him while he was taking his last breath."

"Then she texted my niece a couple hours later, 'Hey, do you know where your brother is?' Then she texted his mom the next day, 'Oh, hey, have you heard from Conrad?' Knowing all along," she said.

Carter also organized a fundraiser for Conrad Roy. "All of his family showed up. Making all kinds of Facebook messages, tweets, talking about how he's her angel and she misses him, and she wants to be this advocate for suicide prevention," Bozzi said. "That, to me, was really where it got, we're not dealing with a normal human being. ... I think she just has a damaged moral core."

Bozzi said she wants people to know that her nephew "wasn't a troubled young teen, that he wasn't suicidal. ... He did struggle. He did have depression, he did have social anxiety and a lot of people do. A lot of boys do. A lot of people don't like to admit it when you have that, because you think it's a sign of weakness, so you don't like to share it. But it's OK.

"Mental illness needs to be further researched and treated," she said. "As far as violence against men, I think is something that gets swept under the rug. I think women bully just as much."

Bozzi said she went to court every day of Carter's trial for her nephew.

"There's nothing else I can do for him," she said. "I know that I know how much he loved his mom and his sisters, and he's protective of them. I just try to watch over him like I know he'd want me to.

"I think the world gained an angel. I think that hearing his story and getting to know who he was, I think he's in his absence just making a huge impact on people's lives," she added. "If it can help a couple people then he's happy. I can see him smiling."

ABC News' Doug Lantz and Joseph Diaz contributed to this report.