I think you should cancel the meeting unless YOU feel you are ready.. if you have exposed this to her mother etc...

Turning away from you to sort things out in private is NOT going to repair this marriage...

have you guys gone to family therapy at all yet? Serioulsy.. one year in and she wants to bolt because some creep is whispering in her ear?

And NO, you do NOT need to PROVE to her with details. You just need to say "I know and I am not an idiot so don't try to deny it. I don't care how far it has gone or hasn't gone... He's in interference in our resolving anything here. As long as you are in contact with him you are NOT going to be able to make a level headed decision here... And I will not stand here and watch you run around with him lying to everyone that he's just a friend of yours either... HE's a predator to our marriage and I want him gone if you expect me to cooperate with you at all."

And ONE WEEK away from him is NOT giong to work.

"I want him GONE form our lives while you and I are IN each other's lives. If divorce is going to happen then that's AFTER papers are signed and that's a LONG WAYS away from now. If we reconcile and rebuild then he is NOT involved with you in any way shape or form becuase he is marriage-hostile and isnt' welcome in our home or in EITHER of our lives."

If you want to explore this marriage and its merits with a famly therapist I am 100% on side with you there... And I will do whatever they ask me to do... But OM is NOT a family therapist and he is NOT in ANY WAY safe to be talking to right now... He is JUST going to be a HUGE interference here and I want him gone before I agree to giving you space to talk with a family therapist. If you want me to move out while we are in Family Tharapy I am in favour of htat.. but NOT if you are in contact with him in any way."

And just walk away.. Don't back down from that sort of position.

If she tries to negotiate you tell her you are offering her family therapy and the space she needs as well as the run of her home... Tell her she can have a MONTH if she's willign to go to FT for that month... etc But NOT while she is frolicking around with OM... NO NO NO