my friend is being abused

My friend has been mentally and physically abused for years now. They have a baby together and I think she feels trapped. He tells her to kill her self, throws tables at her, punches holes in her walls, but she won't leave. She won't get help. She won't call the police. I honestly can't sit back and watch this happen for the rest of her life I'm so heart broken. I can't help someone who won't help them self but I honestly don't know what else I can possibly do or say. Please help.