Carter also allegedly texted Roy telling him to "get back in" to his auto prior to his death, after he reportedly texted her expressing hesitancy and worry.
The judge said instructing Roy to get back into the truck was willful and wanton behavior. She texted him again, encouraging him to follow through.
The judge presiding over the case reviewed extensive evidence, including thousands of text messages sent back-and-forth between the couple, and eventually ruled that Carter did little to stop Roy from putting himself in harm's way.
He continued, noting that Carter failed to tell anyone of his plans nor to "issue a simple instruction to get out of the truck".
Sobs broke out throughout the courtroom when the verdict was announced. She also isn't allowed to leave the state.
She faces up to 20 years in prison when she's sentenced. She is due to be sentenced on August 3.
Texts messages which were presented in court make for harrowing reading, as the accused urges the deceased to act on his intentions.
Roy killed himself in 2014 by starting a personal generator in his vehicle after Carter sent him hundreds of texts encouraging him to do so.More news: UK Parliament: At least 90 email accounts hit by cyber attack
What do you think of the verdict? "You just keep pushing it off to another night and say you'll do it but you never do".
"I'm done", Carter wrote in one message shown in court.
In her defense, attorney Joseph Cataldo told Judge Lawrence Moniz she believed she was helping Roy and couldn't be held responsible for his death as she was operating in a fog created by medication.
The judge said he did not take into account in his verdict Roy's previous suicide attempts.
An involuntary manslaughter charge can be brought in MA when someone causes the death of another person when engaging in reckless or wanton conduct that creates a high degree of likelihood of substantial harm.
The lawyer said that she only started supporting his suicide after being "involuntarily intoxicated" by antidepressants.
According to Bristol Assistant District Attorney Maryclare Flynn, Carter had asked Roy more than 40 times when he was going to commit suicide.
The judge's decision surprised many legal experts, who had said that, despite the callousness of Carter's conduct, the case presented a stiff challenge to prosecutors because MA, unlike dozens of other states, has no law against encouraging suicide. You need to do it like you did last time and not think about it and just do it babe.