I am not sure that I am prepared to deal with this right now either, so deferring gives me time to finalize what I am going to say to her.
I agree with everything you have said especially regarding the consequences. She and the OM need to know that their actions will generate some negative impacts for our family especially our kids.
She is very concerned about what impact a divorce may have on our kids. Choosing her kids over the OM is a more likely outcome then choosing me over him, but at least that would remove him from the picture.
The other issue is that they work for the same company, so allowing this to continue unchallenged is problematic. She did apply for a job with another company last week which I wasn't aware of when I confronted her about the OM. Maybe this is a good sign.