I have said this here before, and many of you may be sick of hearing it, but it is an all consuming thought: part of me thinks I should continue to GAL, be here for her when she needs me (which does not seem likely), and hope that she comes out of her depressive fog at some point, and part of me says I should listen to our mutual friends and walk away and not look back.
AC-
You can do both! Maybe you can't see it now, but you can. This doesn't need to be absolutely resolved in you all at once. Even if you wanted to, you can't force it to be resolved. You can move on, live your life, yet occassionally look back. If enough time goes by and you see no change, the time between your looks will get longer and longer, until eventually you notice you're not looking back any more. Then, maybe then, this will be resolved in you.
What if she was in the military, and was sent away on a six month tour of duty, one where she'd have no opportunity to contact you. What would you do? You'd live your life, and that's what you should do now. Think of it that way if you need to.
I will say this though, as I have said to you before. Do NOT let her come swooping into your life, and lay a big fat, oh-woe-is-me, it's-all-your-fault, goose egg in your lap whenever she wants. If she tries, stop her in her tracks and tell her you accept responsibility for your part in the collapse of your marriage, you are working on yourself, you are willing to work with her on the marriage, but you are NOT willing to let her dump her garbage on you. Then go about your business and live your life.