Would you just forget about your sister?

If shes in an abusive relationship, and shes back and forth with him? She separated from him like 10x, she has 2 small kids with him, and she's also pregnant. She keeps going back to him and they always have problems. He's always mistreating her, he cheated on her, and he's abusive to her in all ways. All my other brothers and sisters doesn't want anything to do with her anymore. And my parents are having enough of it too, they said if this time she goes back to him, they're not going to accept her in anymore the next time she runs away again from him.

I feel like I'm having enough of it too, it's a cycle where she keeps leaving and going back. Should I keep letting her into my house all the time she gets away from him? Or forget her?