I'm sorry that you're here, she's been having a boyfriend for 9 months and claims she didn't have sex, if you believe that I have a bottle of magic air I want to sell you.
She says she won't talk to him or see him and is wants to go to counseling to try to make things work.
Oh how nice of her, now she says she won't talk to him or see him, tell her that was what she was supposed to do in the first place, but instead she CHOSE to cheat and betray you and the family. Workplace A's are notorious for "lunch quickies" and BJ's and/or makeout sessions in the car or at a nearby motel, just tell her she's got 30 seconds to come clean, otherwise you will be filing for D the next day. Here's a few of the basics:
1) She needs to end the A, just because you found out, doesn't mean it will end on its own, if they work together, one of them needs to quit. She needs to send him an NC FOREVER letter that you approve of and watch her hit send, (no sweet goodbyes), if any of her friends or family knew about it, they're not friends of the M and need to go too.
2) Inform OBS (Other Betrayed Spouse) without warning, also EXPOSE her A with ALL family and close friends, she needs to apologize to them too for her huge betrayal, again do not tell her you're doing this, just do it, she needs to feel the embarrassment and remember the A as the one thing that damaged her reputation and integrity and not remember it as something "beautiful and romantic", the more she hates the A, the more she will hate her AP, the less likely she will be to cheat again in the future.
3) This was not your fault, problems in the M you own 50/50, her A was 100% her decision and choice, she literally lied to you thousands of times to keep it a secret and carry it out, she took precious time away from you and the family, you will have some tainted memories of it forever.
4) Consult an attorney to know your legal options and see what D looks like, at a minimum have him draw up a postnup in your favor and demand she signs it as a condition to try to R, if R fails and/or she cheats again she doesn't get alimony/spousal support and won't touch your retirement.
5) Demand she gets tested for STDs, you should too, some STDs can even be transmited via saliva (kissing).
6) Demand she gives you a complete timeline of the A with all the details, if you are to forgive you should know what you're forgiving.
7) She needs to agree to full on demand access to her phone and all her electronic devices and passwords, no questions asked.
8) Demand she goes to IC with someone who specializesin infidelity (very important), MC is typically a waste of time and money right now, she needs to find out her "whys" and deal with her own issues first.
9) She needs to show true remorse (not just regret), you cannot R with an unremorseful spouse.
10) Demand she takes a polygraph, remember she's now a proven cheater and a liar and this may not be her first rodeo.
11) Don't believe anything she says and watch her actions, did I mention cheaters lie and trickle truth ? She's in self preservation mode and probably wants to rugsweep the whole thing.
Also know that this may be a deal-breaker for you and that's OK too, cheaters are not entitled to a 2nd chance, they CHOSE to break the M vows, don't let her tell you this was "a mistake", she made thousands of conscious decionns to betray you for 9 months (that you know of), she willingly cheated on you.
Keep posting, this is a crucial time, we've seen this play out literally thousands of times here and other websites, the collective wisdome of SI can help you navigate this awful situation.