DOC said
I think her full disclosure is a cry for help. Otherwise, she would have just kept it a secret or packed her bags and left.
I disagree with the above for the simple reason I've been around guys/gals were they had flings such as this and the overwhelming reason they "fessed" up was because they know how most guys are about not being able to keep something hidden/secret and actually bragging about it to other guys/friends about their latest conquest/triumph or "notch in their belt".
It's your life and you can view what happened anyway you want, BUT you've heard the saying," fool me once shame on you, fool me twice shame on me."
Think about the deceit involved here. It wasn't one of those times at work or some other location a guy gives a girl some attention and she has been feeling kinda low about herself and lets the guy maybe touch her boob or butt etc.. and then feels either guilty or ashamed that she let it get to that point.
No your wife from what you described deliberately lied to you (going out with the girls etc.) then intentionally wore a lingerie bra to expose her nipples. (that shoulda been a what the hell moment for you)
I wish you the best of a bad situation and only you have to live with your decision but I can't shake the feeling she was more worried about someone else OUTTING her than just being honest about what happened.