Domestic Abuse

Here's the situation: my best friend is 5 months pregnant and in an emotionally abusive and border-line physically abusive relationship. We talk about it regularly, I've called it what it is, she knows he's abusive- but she won't leave him. 
I truly hate what he does to her (tells her he doesn't love her, steals from her, calls her names, shoves her when she tries to stand up for herself, the list goes on), but right now I'm more frustrated that she just takes it and does nothing about it. I know I can't make her leave him or make her stand up for herself so for now I mostly just remind her of her worth. I tell her how great she is, how much I love her and how much she deserves someone who treats her with respect.
What more can I do? Is there anything else I can do? When/how/should I contact the police at any point? How does this work??
**remaining anon for her privacy