Based on what you've said about the conversation with your W, she is trying to be honest about it. It must have been awful to hear her actually say she loved the OM. But here's what I noticed that may be a bit different with your stitch (not that it doesn't happen, just doesn't seem as common) and that is saying she loved you also. So many times the W will have such negative feelings toward her H that she doesn't feel love emotions for him. Or as some experience, they are given the "I love you but I'm not in love with you" speech. So try to take it as a positive sign, but don't try to dig for more right away. B/c her feelings are really confusing for her. If she's got two great guys who want her....and she has feelings for both of them, try not to question her further on that point (and it will be hard not to ask again). Remember, every time you ask her about it, you are pressing her to make a choice right then & there. Even though it seems as if your M should not be an "option" and she shouldn't have to "choose", every time she's pressed by you or anyone else....she feels she has to make a decision at that moment. You don't want her trying to make decisions when she doesn't even know her own heart/mind right now.
I wish I could tell her that I was probably the most straight-laced person ever! I was the last woman on earth anyone would have thought about having an interest in any OM. It can happen to anyone. Yes, it is through our own free will, but given the right (or wrong) circumstances and going without certain needs met for so long can make any person vulnerable to the attention of another one who seems to care about us. I was not informed about all that brain chemistry that caused the same "in love" feelings when having an A that was similar to how I felt when I really fell in love with my H. But one way to know that it is an addiction is for her to go without seeing/contacting him....or know when the next time will be. It won't take her long to realize it. You see, she could make it through the weekend b/c she knew once Monday came...she would be seeing him again.
An A is built on secrecy and deception. It is a fantasy where the A partners see each other looking and acting their very best. They don't have to deal with the down side of reality that you and she faces all the time. They have a "select" time together. Once that is taken away, the excitement leaves with it.
I hope she will find another place of employment for the sake of the M. But I think OM will make it difficult for her to just walk away.
I'm glad the two of you could talk. However, I know how she feels about not wanting to discuss certain things with you. It may be best that you don't ask for every detail, IDK....everyone is different. But the more you know, the more you will have to overcome and get past it. After time has gone by, you may discover it is more than you can handle. Allow yourself time to digest a little before asking for more.
Oh, and about the M or the OM being an option. For me, it was like I had the idea he was my last chance at real love. "What if this is my only chance to be really happy and I throw it away?" Like I said, her feelings and mindset are very mixed up right now. I know it has to be hell for you, but rest assured, it is for her...as well.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!