Mike, It sure seems like you are getting played. DETACH. Credit Card bills for an affair, you need to end that, if it is a shared account close it down. I am a tough love advocate, so stand up for your self and get a life. Go out with your friends, have a great time. Make yourself scarce and have other things to do.
I think Sandi is right on everything. You are setting up to be the BFF, is that what you want? She is trying to placate her guilt and you are buying it.