NYG - I don't think it is on you to "let this go".
I'm not sure you should DO anything just yet.
But you can't just allow this boundary to be crossed without any issue. What if W said she just needed to sleep with OW one more time "for closure"? Would you be expected to just "let that go" too?
This is about you now. I think your sole focus has been on repairing your R with W. What do you need to heal?
