Stuck...I will be back and address your questions shortly.
Sweepsr....you said: "She cried that she keeps destroying everything good in her life."
To me this is the most important part of your post. When a person is self-destructive, you cannot do anything about it. You can try to help, but they will turn your help around and hurt themselves and others with it. She has to be left to face her problems on her own.
I know that you are a kind-hearted man and you sincerely want to help her. But because you are not a self-destructive time machine, you simply cannot fathom what lengths she will go to to destruct herself. Being kind is not going to help her, no matter how you wish it would. If a friend found YOU in need and was kind to YOU, then it WOULD help you. But that is because you are not a self-destructive time bomb.
We can't apply certain types of help to certain problems, yet that is what you are doing. You are trying to help her with kindness, yet this will not have any effect. If anything, your kindness toward her when you SHOULD be angry at her, will cause her to further self-destruct.
She knows that she is being unkind, hurtful, and downright cruel. And she is struggling to try to figure herself out and find out why she does these things. In order to TRULY help her, what you need to do is step aside and allow her to feel the consequences of her actions. THIS is the only thing that may cause her to change and try to help herself.
As long as you allow her to place you in the "friend zone" and you listen to her pitiful stories, she cannot be helped by this. She can only feel worse and worse about herself, and have less and less respect for you because you are helping her self-destruct.
You are such a good person, and it is so difficult for a good person to respond in a way that to them will feel cruel. So to you, it would feel as if you are being cruel if you simply told her "sorry hon, I can't listen to your story any longer, you'll have to find someone else to talk to". You would feel like a bad friend to do this. You would feel like you are being cruel or possibly forcing her off a ledge and you would be afraid of what she might do next. BUT...this is only because you are not a mental health professional and therefore you can't imagine all the ways that you are currently enabling and approving of her self-desctructive behavior. You think you are being kind, but in fact, you are helping her keep in a state of non-growth and limbo by enabling her bullcrap.
So be a good man, not a nice man. Do the right thing, not the easy thing. It will not be easy for you to set a boundary upon her and not listen to her anymore...but that IS the right thing. The right thing is rarely the easy thing.