Friend In a bad relationship

I have this friend it starting to look thta her relationship is becoming verbally abusive and the partner is manipulating her. There has been threats he's made against their kids. She left then got back together with him but lives with her mom. Her family doesn't like him and they actually secretly got married a couple months ago. Her mom was furious.

I had told our mutual friends if we go all go out and tell her the concerns. They don't want to do it and I really don't know too much. I was thinking about writing her something. Should I say something or no? The other friends have mentioned things to her and she doesn't listen. I can see them giving up on her.