involuntary manslaughter in MA requires an act that causes the death of another and that act must be wanton and have disregard of the obvious consequences.
She committed no act that caused his death. He killed himself. Words are not an act.
The charge can also be the result of failure to act, but again, she was not even there. If she watched him get back in the car and watched him die and did not call the police or try to get him out of the car that would be one thing, but again she was not there.
All she did was text him. She used words. I do not see how that rises to criminality of an act that causes a death or an inaction with a legal duty to act, as the case law states.
If this case goes forward, it means if someone texts you something that sounds like they will get hurt, like they are texting you while driving, you will have the legal obligation to call the cops. This is stupid and may have far reaching consequences, but I am not an attorney.