So how does she expect to 'heal' if she's still doing things to appease her ex boyfriend? He is *not* her responsibility; he won't kill himself, he's just trying to scare her. But if the worst happened - that would ot be her fault. She's not responsible for his mental problems, drug addictions and what not. If it's over, it's over.
The only person making her life more difficult that it has to be is her and that's because she's not clear on her feelings. If she felt nothing for her ex and wanted nothing more than to be free of his drama - trust me, she would cut him off regardless of how many telephone booths he crashes into. He's not the problem, she's the problem.
If she's having a hard time (mentally and emotionally), she should be seeing a therapist. The last thing she should be doing is having any contact with her crazy ex.