My friend is with a bad guy.?

My friend who we can call "Sarah" met this guy on the internet, we can call him "Josh". He asked her to be his GF and she agreed. The two were dating fro a while, but now she is changing. She's telling me and Katie (Our other friend) that she loves Josh so much and that he's everything to her.She's letting him control her life. She says that she would do ANYTHING for him, even if she didn't want to (If you catch my drift) and if he left her, she would seriously consider suicide. He has cheated on her with multiple girls in the past and she knows about it. She says that it's a phase he's going through and that he'll change. Anyway, he asked her to send him nude pictures and she did! :( The Sarah I knew would NEVER do anything like that. He controls everything she does and she lets him. Everything HE says is right in her opinion. She was looking for a job and he told her that women shouldn't work, that they were meant to have the kids and be house wives. She cried about it, but is still with him. We've tried everything. We've warned her that this was dangerous and that she should leave him. We've even discussed this with adults and her parents even supposedly knows, but nobody is forcing her away from him. She's only 16! I feel that she should be forbidden to speak to a perverted monster like that, weather she likes it or not. I doubt she'd listen if she was forbidden from him, though. She's so obsessed with him. She really thinks that this is love, but if it is love, why does she cry about all the mean things he says to her? Why won't anyone force her away from him? She plans to meet up with him when she's 18, but I really don't want this to happen. Katie doesn't either, but nobody will really do anything. Are Katie and I the only one with sense around here?! Nobody else seems to freakin' care! As her friend, I can't allow her to risk getting raped or controlled all her life. Josh seems like he'd be the abusive and perverted type, considering the things Sarah's told me about him. Why is she allowing herself to be treated this way? Is there anything I can do to help her? I've talked to her about it, but she refuses to leave him. I know that I seem like a controlling friend, but I've known her for so many years and I'd die if anything caused her any type of harm, weather it's physical or emotional harm. In this case, it's both.