Advice needed !!!!

Guys, how do I help someone who doesn't want to be helped??? I have this girl, and she's mentally unstable, and she doesn't take care of herself, or anything. I give her advice, and everything, but she just wants to sabotage herself. I want to help her desperately, I try to, but I don't know how to when she won't listen to me. She doesn't eat or sleep enough, she doesn't take care of herself, and it feels like there's a small gap between us that wasn't there before. I don't know what to do.