I would NOT discuss this tonite, for a couple of reasons. One, that's her timetable, not yours. She's not setting your agenda now. Two, you need time to process this emotionally -- you've been hit with quite a bomb, and you need time to think, pray (if you're so inclined) and gather advice from a close circle of those you trust.
See my other post to you about this. If she wants to talk tonite, say "I'm sorry, I'm not ready to discuss this yet. I have some thinking to do," or some such.
I'd also suggest saying something along the lines of "I have no intentions of discussing this marriage so long as you've unilaterally invited a third person into it. End your affair, and I think you'll find me ready and willing to discuss all issues, including mine."
Let her sweat a bit. And WHATEVER you do, DON'T MOPE. If she asks you how you are (some do), say "Me? I'll be fine. I just have some thinking to do," in a matter-of-fact, confident voice.
