I want to put someone in prison for encouraging my girlfriend to kill herself, but I don’t want my girlfriend to have to appear in court or testify. Is this possible?

I have all the evidence, and my gf has more. I texted with this person for just a little tonight and I hate them with a passion. They have openly admitted to wanting my gf dead and that they’ve tried to get her to kill her self before. I have screenshots of all that. I don’t want to use much if any of the evidence my gf has, that’s really traumatic and not something I could ask her to do. Is there any way to get this person in prison? They are a minor in Massachusetts