I really feel like your post is an honest, clear, and insightful look at the whole situation. The way you handled it is very likely best. I know you feel a little guilt, but you both have to take care of yourselves before you can take care of each other. You recognizing the co-dependency thing is a huge step, and you did the right thing. That doesn't mean you can't be there for her as a friend, if she'll have you as a friend. I don't know how long ago this happened, but maybe you could check in on her and see how she is doing and if she needs a friend to talk to you can be there for her in that role, as a friend.