Hey NLG - my situation was a bit different than yours, but when we were out in public and around friends or family, he was a different person with me. Touched me more... acted like nothing was wrong. Messed with my emotions a TON!!!
I guess you ask yourself why she's doing these things. Is she not wanting the freedom anymore? If so, are the things she's doing enough? Are you willing to give her a final chance?
If you are, set the ground rules again. Absolutely NO CONTACT with the OM... AND you'll need proof. She'll have to be transparent, willingly for as long as it takes for you guys to rebuild that trust. Couples counseling and IC... etc.
If not, enjoy the extra help... continue detachment... stick to your guns and make her MOVE OUT!!!
It takes three to five years to get over something like this... I wish it could be faster but I guarantee that this time next year... heck in just a few months... you'll notice a difference. No matter how small... progress is still progress. it is up to you how you will live your life from here forward.
When you are happy as an individual, you are in a better position to determine whether a partner enhances your happy life or weighs it down.