You are not going to give up so put that out of your mind. You know that and I know that.
Secondly, I hate to comfort you on the point of cheating because it's really the one think I DON'T like about you but I will anyway because of all the other things I think I DO like about you. What I am trying to say is that while you may have "cheated" I don't see much difference between that and what she may or may not be doing "out late" with her "friends".
This is not a tit-for-tat contest but from where I sit, that's what she's doing and is sucks. You have remorse for what you did, she is willingly doing it, all the while claiming to be a victim of YOU. BS. She is not a victim any more than you were so she needs to get over that.
I am not saying you are even with her but something's gotta give, and as you said, reality WILL set in for her. I think your campaign of self-improvement and patience WILL pay off. I have to believe that because this path of destruction she's on should give out sooner or later...hopefully sooner.
Keep your chin up, pray, read and pick yourself up. You've done it before and you'll do it 1000 more times before it's all said and done.