Abusive relationship advice

Alexis

My sister is in an abusive relationship with the father of her child. I need help convincing her to leave for both her and her babies well being. Her friend just texted me saying she witnessed him hitting her so I called the police but I don’t know if the police will actually do anything if there are no actual marks on her and she doesn’t admit to it. Any advice on what I should do I’m extremely worried about her