MH,
Although she has told me when I ask that she isn't seeing the OM. (I didn't ask on Sunday) So I guess she thinks that I'm buying that even though I know different.
What I don't know is what she is telling the OM.
If you have definitive proof that she is living with the guy, or seeing him, then you really should tell her, and ask her why she is hiding it. And, as you yourself say, ask her what she is telling him about her visits with you. Is she lying to him too?
The point of this is not to start a fight, but for you to let her know what you know, and that it is not fair or right to be telling you things that aren't true or giving you false hope. And that is how to put it, if using the word 'lie' feels too emotive.
I have mentioned before in this thread that her relationship with her manager is unlikely to be well-received by their HR department, and so she has to be very careful to ensure that you do not contact HR with your story and evidence. If she is living with the guy, or actively seeing him, the HR thing is a very good reason indeed for her to be telling you there is no relationship. You haven't said how you know their relationship is still active, or where she is living, but while you are hoping for the best, it may be just as well to prepare for the worst and get either you or a private investigator to get some documentary evidence of them co-habiting. Like pictures of her car outside his place several times, pictures of her going in and out, etc.
Her not telling you the truth on this aspect is very significant, because it could lend itself to her moving back in with you and continuing to the relationship with the OM during work time. I know you love her, but she may simply be cake-eating at the moment, and bouncing between two men in her life.
The point is, what your life, and your relationship with her needs, are clarity and honesty. At the moment, you are getting neither. So if she is lying about the state of her relationship with the OM, you need to get and compile your evidence that proves they are still together, and let your wife know that you know. Until she can start being honest with you again, could you trust her if she said she wanted to move back in, and was then going on lots of business trips with the OM again?
I think she's being very 'cute' here, controlling things by carefully managing what she says, and what she doesn't say. Even though you are effectively in a position of being willing to accept her back if she finishes the affair, I really think you need to take a stronger stance than that. That does not mean being aggressive, it means standing up for your right to be told the truth.
Without truth being brought back into the way she relates to you, how can you ever have any faith in the affair having ended? Wanting reconciliation is fine if that is where your heart is, but you have to bring your head into the game too. If you make it easy for her to live by the lie, the half-truth, or the omission, and you accept her back under those terms, what kind of reconciliation will it be? One where she continues to see the OM, but tells you it is all over, while you know different?
I guess what I am getting at is that no matter how much you would like her back, it is not in your interest to let her back unconditionally, because it will only lead to more pain for you if she comes back in a cloud of misinformation and continues seeing the OM. The only people that will suit is her and the OM. So if you know she is lying about anything, you need to call her on it, because not contradicting her just so you have a 'nice' dinner is effectively telling her it's fine to base a reconciliation on lies. We all know it isn't. And there is no reason why you cannot reconcile if she starts telling the truth, is there? I know you probably feel like you don't want to say or do anything that might rock the boat, but sometimes the boat needs to be rocked, to get rid of the unhealthy element of dishonesty that will just cause problems in future if it is allowed to continue.
Would you really be out of line to say something like, "You know that I love you, and how unhappy I have been about us being apart. You know that I would like us to be together again. However, that can never happen if you continue to be dishonest with me. I would far rather you be honest with me and hurt me than lie to me and make me a fool. At least do me the courtesy and respect of telling me the truth, whatever else you may think of me."
Yes, you want her back, but you need to look out for your best interests too. Don't let a liar waltz back into your life; instead, consider reconciliation with someone who has come far enough out of the 'fog' to start treating you with the basic respect that all human beings deserve. That can happen, but only if you make it clear to her that lies and omissions will prevent that from happening. Honesty has to be restored before a meaningful reconciliation can begin, and now would be a good time to start working on that, before there has been any serious talk of the future.
Whether or not this was a mistake on her part, it will be a mistake on yours to give her the impression that it is fine to lie to you, whether you reconcile or part ways. And if you stand up for yourself, and you are not a pushover, she will respect that, and bringing respect back into the dynamic between you is also important. That doesn't mean being Schwarzenegger, it means politely asserting your rights, starting with the right to honesty.
I'm hopeful for you, MH, I just think you need to be your own best friend here and set out your boundaries and needs. The woman you want back should be a remorseful and honest person, not a lying cake-eater. It is your choice about which one you let back into your life if reconciliation does become a prospect. We both know which one you should choose!