My friend's "bf" has her as a prostitute

Ok, so my best friend is in some kind of "relationship"(using that term very loosy) and her "bf" is her pimp. She's a prostitute now, "willing", so that she could "be more close" to him. He works as a pimp and drug pusher. Since day one of her meeting him I warned her to stay away from him, now she lives in a motel, pretty much as a prisoner, she has gone days without eating!!! Her whole family knows whats going on, they pretty much alienated her. Her mom would sometimes show up and give her food, but their relationship is not that great. I CANNOT be suportive, and she REFUSES to leave!! She does not get paid, she hardly sees her "bf". She has no one, but I'm getting very tired of the same shit, she complains but never leaves. She claims to love him and that its hard for her to leave him...every single phone call we have its the same shit!!!! Her complaining but NEVER leaving!! I don't know what to do!! I want to stop talking to her until she leaves that arsehole!! Should?? Or should I keep "being there" for her? Her family pretty much leftbher alone, she has no one and I don't wanna leave her alone, but she can't see how self destructive she's being!! Idk what do you guys think, should i give her the ultimatum, either she leaves him or i stop talking to her until she gets her crap together?? Saddly i know she won't leave, even if we've been friends for almost 15yrs :(