If you're wife is choosing a friend over you, then you're not the number one dude in her life.
I'm not sure its quite so black and white.
Yes it is. It is exactly that black and white! If the wayward is claiming the OM is a "friend" and that's all he is.........then there should be no confusion, no complexity, no hard decision choosing your husband and marriage over some so-called friendship. Truth is that it's not a friendship at all. It's an affair.
Look, the WW will mess with your head and make you think you are the unreasonable person in this triangle she's made in the M.
She had absolutely no problem "seeing" how a close friendship with your ex would not be healthy for your MR. So don't go off the rails trying to make an exception out of what she's doing now.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!