I agree with this, but I think in the OP's scenario, she was saying it was inevitable. Not sure if this would change your answer.
I'm going to say this on this thread and on the other cheating thread.
While I do believe it's POSSIBLE to have monogamy in a marriage, I will be 100% honest and say, I do believe that there are genuine pros and cons to both monogamy and "polygamy" (polyamory).
I don't see one or the other as being a perfect way to marriage. Both will require sacrifices (albeit different ones), and both honestly have benefits. I think each couple has to decide what is most important to them in marriage.
For some people monogamy is a requirement and without it they can't be married. For other people, if a man or woman cheats, it doesn't have to be the end of their marriage. And there have been many couples where infidelity has happened, and their marriage ultimately becomes STRONGER after getting through it!