Better to lose half ones stuff than to be in a passionless & sexless marriage with a crony. Of course the truth is...he created that passionless cohabitation. I think that’s the real point on this forum.
Couples in a marriage should always strive to be the best version of themselves not only for themselves but each other.
I mean if the trade off is monogamy then step up lady lol. This is what I can’t get my head around, instead of trying to meet his needs because he’s her husband she’s passing it off almost like it’s a headache that she would rather not deal with.
Or Maybe they were never sexually compatible and now that the kids are grown she feels that part of the marriage is done. Maybe she just got tired of him for whatever reason. We don’t know and OP is not giving us much of a back story so I’m just speculating of course lol.
But this is like the stuff that happens when married couples stop dating each other and become roles, rather than two people who compliment each other and are connected as a couple, not just as parents living in the same home.