RF: I urge you in the strongest way possible to at least do the following:
1. Have her WRITE a full timeline of the entire process, from the moment she STARTED planning this excursion (note: there’s likely far more - we’ll get to that). Only give her 1-2 days to complete that. If she gives a damn about the marriage she’ll get this done within a few hours of you asking. Demand she get extremely specific and explicit for EVERYTHING including every sex act, how she met AP, every flirt, every conversation, everything.
2. Have her READ her timeline to you. Tell her she’s not allowed to be filled with self-pity while she reads this to you. Obviously, you keep a copy of the timeline. This is critical so she can’t spin any future lies like "I already told you that - you forgot".
3. Tell her she will be taking a polygraph to verify the veracity of the timeline. Tell her she will be paying for the polygraph by selling something personal of hers that’s meaningful to her and using those funds.
4. Have HER schedule a SERIES of STD checks for the both of you (some STDs take multiple checks over months to verify). Again, she pays for all of them similarly to #3 above.
5. She agrees to sign a post-nuptial agreement that favors you. Others here will tell you they are worthless, but her acquiescence (or refusal) will tell you something about her remorse. Absolutely get a lawyer involved and have a video recording made of her signing it of her own free, clear-minded will, so you can lessen the chance of her later claiming she signed under duress.
6. She agrees to tell her parents and siblings (if any) exactly what she has done, with you present. Don’t let her spin up a false narrative or blame-shifting on you. You decide whether she must also inform your family.
7. Follow thru with the polygraph (unless you’ve decided on D, in which case who cares). Moments before walking into the poly, ask her if she has anything else to tell you before you start. Unbeknownst to her, have the examiner also ask her whether she’s IN ANY WAY been unfaithful in ANY WAY during the entire time of your relationship.
8. Demand that she identify this AP. If she "doesn’t know" then it’s her mission to find out. That said, she is under NO CIRCUMSTANCE allowed to contact him. Once found, if possible, inform AP’s wife or girlfriend.
9. Any "friends" of hers that knew ANYTHING about this and didn’t tell you are now dropped forever. ZERO contact, other than to tell them she will never interact with them again.
10. She agrees she will never again enjoy ANY kind of device, social media, or location privacy EVER again.
If it’s not obvious, her words are now meaningless. Only her actions matter. If she doesn’t immediately agree to ALL of the above, initiate D paperwork. NOTE: at any time if she gets her head out of her ass and FULLY agrees to do ANYTHING to save the marriage (including all of the above), you can always pause or stop the D.