That sounds like it's ok for her to see him - as long as you also have plans.
And is withdrawing and not engaging with her really all that much of a consequence?
Without looking back...
Is she still in the marital bed? Do you still ML? Do you still do other things for her?
Clearly you are still living together, so that's an area to consider.
I think what you are trying to say is - this is disrespectful and painful to me and I am not going to tolerate it. If it continues, I will do X. Fine, I understand that. But what happens as a result? Does she have to move out of the marital bed? Get her own place? Do you close the joint account and she has to fund her own stuff?
The thing with consequences is they need to link back to the boundary. ie: if you continue seeing OM in this way, you will have to move out and get your own place. It is painful and disrespectful for me to see what is happening and we can not live together if it continues.
Have you read Wonka's boundaries cheat sheet?
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus