Lawyers for the 22-year-old Carter have said they plan to appeal to the US Supreme Court.
The judge found Carter caused Roy's death when she instructed him over the phone to get back in his truck, where her later died.
Carter's lawyers say she isn't responsible for Roy's suicide.
Last week, the judge said Carter, now 22, had a duty to call the police or Roy's family when she knew the 18-year-old intended to kill himself.
"Then after she convinced him to get back into the ... truck, she did absolutely nothing to help him: she did not call for help or tell him to get out of the truck as she listened to him ... die,' Justice Scott Kafker wrote in the Supreme Judicial Court's ruling.
Carter's lawyers noted the only evidence she instructed Roy to get back in the truck was a long, rambling text she sent to a friend two months later in which she called Roy's death her fault.
Carter was 17 when Roy was found dead in July 2014.
The young woman was sentenced to 15 months in jail but has remained free while she pursues her appeals.
Prosecutors had argued Carter could have stopped Roy from killing himself, but instead bullied him into going through with his plan through text messages that became more insistent as he delayed.
"I thought you wanted to do this. The time is right and you're ready - just do it babe," she wrote.
"You're finally going to be happy in heaven. No more pain. It's okay to be scared and it's normal. I mean, you're about to die," Carter wrote in another.
Carter's lawyers argued she can't be convicted because of her words alone, noting she wasn't with him when he killed himself and didn't provide him with the means to do it.
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
OR IF YOU NEED TO TALK TO SOMEONE ELSE:
• 0800 543 354 (0800 LIFELINE) or free text 4357 (HELP) (available 24/7)
• https://www.lifeline.org.nz/services/suicide-crisis-helpline
• YOUTHLINE: 0800 376 633
• NEED TO TALK? Free call or text 1737 (available 24/7)
• KIDSLINE: 0800 543 754 (available 24/7)
• WHATSUP: 0800 942 8787 (1pm to 11pm)
• DEPRESSION HELPLINE: 0800 111 757 or TEXT 4202
- AP