The cousin of Conrad Roy, the Massachusetts teenager who killed himself after receiving text messages from his then-girlfriend, Michelle Carter, who encouraged him to commit suicide, said she is not satisfied with the Carter’s recent prison sentence.

On Thursday, Carter, 20, was sentenced to 2.5 years in prison for involuntary manslaughter. However, Massachusetts Judge Lawrence Moniz granted Carter the right to remain free while her appeals trials are pending.

In an exclusive interview with Good Morning America, O’Donnell said she feels “sick” about the sentence.

"I was just sick, just sick to my stomach [over] the fact that she can be free, and my cousin, he's not here," O’Donnell told GMA. "She should be behind bars.”

In 2014, Roy killed himself by locking himself in his truck while a tube pumped carbon monoxide into the vehicle. Several months before the suicide, Carter texted Roy and pressured him to do it.

Carter was found guilty by Judge Moniz in June for behavior he described as "reckless." As Judge Moniz read the verdict, she said Carter instructed 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."

While speaking with GMA, O'Donnell added that she believed Carter's sentence is "not enough."

"I just don't understand how someone can be free knowing that she deliberately told him to get back in the car and she gets to sleep in her own bed tonight. She gets to eat breakfast; she gets to wake up with her family," she told GMA. "Meanwhile, where's Conrad?"

O'Donnell also said she believes Carter "needs help."

"No normal human being who doesn't have problems would tell someone to get back in a truck where it is a toxic environment," O'Donnell said. "I do believe she needs help, and I do believe she needs to take responsibility for her actions."