Like everyone else, I'm very sorry to hear the latest developments. Still I continue to believe I have a good sense about your sitch - perhaps because parts mirror my own from years ago.
So first off, I really think you need to be sure. You've not provided much in the way of details about why you think she's talking with OM again. The thing is, we can all be wrong even when we have a strong gut feeling. This is too important not to be positive so I strongly support you confirming it with proof before you confront her.
Once you have that proof, I think you should confront her, calmly, confidently and then say "I'm done" - but only if you truly are. If you are at that point and you totally drop the rope and walk away, I think that may bring her to her bottom. I remember that was the case last time you did this. She all out panicked. I agree with artista. She does not want a divorce and does not want a full on affair. She will get that strong feeling if you drop the rope. She will not want to lose you and the family. Only this time you must make her do the work and win you back.
I of course can't know this is how it will play out but I strongly feel it will. It did with me - for three years anyhow. The problem is, you may not want her back. We've seen that happen here in the past with others. This could really turn positive for you and will certainly get you out of limbo and W will have the ball in her own court. She's playing with fire and getting away with it. When she is caught red handed her feelings may well change and I'm betting on it.
That's my take.
DonH Midwest Me 56 WAW-EXW 55 Met 11/95 / Married 5/00 Bomb 6/20/05 / She Filed on 6/2/06 / Divorced on 10/9/06 4 who'd qualify as GF since D & dated about 25 women since D