The U.S. Supreme Court said Monday that it will not consider an appeal by Michelle Carter , the Massachusetts woman who was sentenced to 15 months in prison for relentlessly pressuring her then-boyfriend in text messages to kill himself.

Carter, who was convicted of involuntary manslaughter in the 2014 death of 18-year-old Conrad Roy, had argued that her actions were a matter of free speech protected by the First Amendment.

A series of text messages sent between the couple on the night Roy died showed Carter, then 17, repeatedly urging a suicidal Roy to kill himself by carbon monoxide poisoning in his truck, even after he told her he no longer wanted to go through with it.