Doing something for a friend

[JP1379]

There's this girl i work with who has become a pretty close friend to me in just a few days, but her parents abuse her and I frankly have no idea what to do. Her mother is bi-polar and will get upset at her for very little reason usally nothing at all to the point of holding a knife at her. She has called the police on her mother numerous times, and they have never believed a word she says. Her father does nothing about this and is usally very mean to her just in general. She has found ways not to be at her house for most of the time, but I can't stand leaving her when she has to go home. I'm a guy and I can't exactly let her stay over at my house, because frankly her parents would kill her for staying at a guys house. She is depressed much of the time, but when she isn't depressed she is almost completly normal and fun. I'm not really her boyfriend or anything, but she calls me to come work with her whenever she's depressed, because she says I cheer her up. I have no idea what to do and honestly don't know how much of her story to believe other than she's called the cops on her mother, because I know a co-worker picked her up outside her house with the cops there.