First understand that marital recovery does not actually start until both parties agree to try and save the M and ALL contact has stopped. So this isn't truly marital recovery. Personal recovery is something else.
To answer your question, it’s true in plan A and life you can’t kill the messenger or she won’t bring any more hard messages.
You are right expressing nothing only enables that A to continue as if it were OK with you. How do you respond, Honestly but tactfully, you thank her for being honest and tell her how you feel about it, what it does to you, what you fear it may do in the long run. Not whining, not crying just as matter of factly as you can. There is nothing wrong with saying you’re angered over it. Anger itself is not a bad thing, acting aggressively, yelling screaming and LB’ing because of the anger is what’s bad.
I’ve seen it go a bunch of ways with contact. Some have continued their plan A in hopes it would make the WS wake up. Some have set it up as a boundary on day 1. That was my tact, my W wanted our M but had feelings for OM. I told her I could work with anything but continued contact and if we were going to try it had to stop then, or I’d walk and I would have. I’ve seen both work and fail both ways so I can’t advise which route is best for you, only you can do that. But remember – NEVER – threaten what you can’t deliver on, so don’t give an ultimatum you can’t live with.
Does this OM have a W? do people know about the A? How far are you in the the book SAA ?
Hang in there,
Oz