Not pregnant related.

This is not pregnant related but I really need advise. My best friend recently had a baby. The father of the baby is not in the picture anymore. So she went back to an old ex of her. She was pregnant with his baby a few years a go but he abused her so bad that she ended up having a miscarriage and now she's dating him again. They agreed to never tell the baby that he isn't his biological father. They got engaged a few months ago. But the thing is.... He is really a bad man! Smokes weed, drink so much spends most of his money on alcohol and weed. He recently told her that she and her baby can go f*ck themselves ( his exact words) pushing her around saying the worst things to her. His very jealous and forbids her to leave the house and if she does he accuses her of not being loyal. A few days ago she called me and told me that he finally came out with the truth witch was he was sleeping with someone else. She broke off the engagement but yet they are still living together and sleeping in one bed. How do I tell her to leave him without sounding harsh? She's very stubborn but I seriously don't wanna see her or the baby get hurt.