MAJOR ADVICE NEEDED!!!

I have this friend. She use to date this guy, their relationship is very complicated. But anyways, they broke up bc he said he didn't feel anything anymore & she refuses to believe him. That was a month ago. & to this day she still doesn't believe him. He says he doesn't like commitment, but they dated for 9 months. She keeps trying to fix things with them, she would do anything for him. Anything he asks, she does. Since she left 3 days ago, he had sex with 5 other girls. She came back, and found this out & figured it was all her fault bc when he told her all he wanted was sex she said no bc she believed he still had feelings. Now she feels like it's her fault he had sex with other girls bc she wouldn't put out since they broke up. Everything he does she makes an excuse for it & makes it her fault. She can't let him go. He's constantly on her mind or she's talking to him. If she can't then she goes crazy. Advice please? I really want to help her, I just don't know how anymore.