Do NOT bring up your W's "hookup", for two reasons at this point. 1) It's gossip and YOU have no actual proof 2) YOU need to show YOURSELF that you can quit worrying about it
Monday's meeting is for you to have a conversation with your W to find out how SHE'S feeling and what SHE wants. That will help you decide on boundaries that you need and decisions you can make.
Be conversational with questions and don't worry. I'm going to harp on you just a little here to drive home a point that I see in you. You say "Monday can't get here quick enough".
There's an element of worry in there. Revisit Coach's quote. YOU will be OK no matter what happens.