No, you are not being selfish. You just need to rest now b/c when your mind starts going in circles like this, it means you are over-analyzing.
I think what you say about how things would probably be for you with her....is right. Only you know if you could or couldn't deal with the past and let it go in order to have a healthy R with her. That kind of hurt takes a long time......even if she came to you on bended knees and crying her heart out with remorse. You might feel sorry for her at that precise moment simply b/c of her emotional state, but then you would begin to remember all the things she did to hurt you......and as you said......it wouldn't be good. So, you may have to go on with your life with the attitude as if to say, "I wished it could have been different, but it isn't, so I must move on." Sad, isn't it? But even after forgiveness....there has to be healing or it just scabs over and the wound is still there.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!