Almost all cheaters are conflicted and hurting inside. Most say things like your W says. "We shouldn't have gotten married". It's all garbage, and they know it. These things are why detachment is important. If you want to fight she will love for you to be the bad guy. She needs a punching bag. If you can be detached, strong ,confident, thoughtful as opposed to emotional and reactive? That changes things bigtime.
H 34 W 29 BD 3/12/18 Divorce Busted Spring 19
It is not things that bother us, but the stories we tell ourselves about things.