WASHINGTON — The Supreme Court on Monday left in place the conviction of a Massachusetts woman who sent her boyfriend text messages urging him to kill himself. Michelle Carter is serving a 15-month sentence after being convicted of involuntary manslaughter in the 2014 death of her boyfriend, Conrad Roy III. A judge determined that Carter, who was 17, caused the death of the 18-year-old Roy when she ordered him in a phone call to get back in his carbon monoxide-filled truck that he’d parked in a Kmart parking lot.

The phone call wasn’t recorded, but the judge relied on a text Carter sent her friend in which she said she told Roy to get back in. In text messages sent in the days leading up to Roy’s death, Carter also encouraged Roy to follow through with his suicide plan and chastised him when he didn’t, Massachusetts courts found.

Carter has been serving her sentence at the Bristol County House of Correction in Dartmouth, Mass. She was set for release in May, but is now scheduled for release Jan. 23, according to a spokesman for the Bristol County Sheriff’s Office. Jail officials said Carter has accrued enough credits for good behavior and attending programs while incarcerated after she was denied parole last September. “Ms. Carter continues to attend programs, is getting along with other inmates, is polite to our staff and volunteers, and we’ve had no discipline issues at all,” Jonathan Darling, a spokesman for the sheriff’s office, said in an email.