Think of it like an addiction. A drunk may hate what he has become. He may say, "one last drink then I am done." But that does not always happen.
I do think she has to show you some progress. She has to.
Ending affairs are tough. Very tough.
It's up to you my man. Either say F it and walk or fight. You cannot choose what she does or does not do. You can only choose what you are going to do.
I will tell you that if my wife would have said F it in the summer, I would be a single man now. That being said, there is a theshold of what you can put up with. Only you can answer that.