A Massachusetts woman who was convicted of involuntary manslaughter for encouraging her boyfriend to kill himself, could face up to 20 years in prison at her sentencing Thursday.

Michelle Carter was 17 in 2014 when she persuaded Conrad Roy III, 18, to kill himself with a series of texts and phone calls, prosecutors said. Roy died when his pickup truck filled with carbon monoxide in a store parking lot in Fairhaven, Massachusetts.

“You can’t think about it. You just have to do it. You said you were gonna do it. Like I don’t get why you aren’t,” Carter wrote in one text.

Carter was tried as a youthful offender, so the judge can commit her to a Department of Youth Services facility until she turns 21 on Aug. 11. He could also combine a DYS commitment with an adult sentence, or can give her an adult sentence of anything from probation to the maximum 20-year term.

Roy’s aunt, Kim Bozzi, said in a statement that is set to be read at sentencing that Carter should be given the maximum amount of prison time, the Boston Herald reported.

“Twenty years may seem extreme but it is still twenty more than Conrad will ever have,” Bozzi said in her statement.

In a letter to the judge, David Carter, Michelle’s father, said his daughter made a “tragic mistake.” He asked for probation and continued counseling.

Joseph Cataldo, Carter’s lawyer, argued that Roy was determined to kill himself and nothing Carter did would have changed his decision. He also argued that Carter’s words were protected as free speech by the First Amendment.

On June 16, a judge found Carter guilty for telling Roy to “get back in” after he climbed out of his truck as it was filling with carbon monoxide.

The Associated Press contributed to this report.