If your idea of marriage is monogamy, which to most people it is, then you can’t make yourself want this. It’s not your problem that she’s suddenly developed fear of missing out, by not having sex with random other men. This is careless and irresponsible on her part, since she’s a grown married woman now, she should have some understanding that recapturing her youth isn’t going to happen. At this point, I worry that she’s already got someone else in mind for this to suddenly emerge as a topic of discussion. Might be worth letting her know that you don’t want to do this, and if she’s still interested in soaring her wild oats, she can do so after a divorce.