How can I help my divorce friend? His ex-wife is always threating him & girlfriend. Wont let him c his kids.?

My friend Norman & Kate are having problems with his ex-wife. She gives him crap about see his daughters. She is always threatening them and even tried to kidnap him. She want to take him to her boyfriends house so he can bet him up. She gives him a hard time about everything. We were hanging out and her she come just to start a fight. No respect for the own of the house (who lucky was not home). Open the door and walks in like she owns the place. I am afraid for my friends and I am even afraid of getting into the fight to break it up. She tells them so many things trying to get them to hit her or something. We are having a Thanksgiving dinner with him and his girls at our home. I'm worred she might start something, she does not care if her daughter see her. Can I do anything threw TX law or something?