So what does she stand to lose by continuing the A? She gets all her needs met and has no consequences, plus has her H waiting patiently until she decides to end things with OM.
I'm glad Sandi brought this up, because it reminded me of something I wanted to say.
While I strongly advocate a betrayed spouse set an INTERNAL deadline (how long they are willing to "stand" for their marriage, before they made the difficult decision of having to file for divorce), I never EVER recommend that you actually COMMUNICATE that deadline to a cheating spouse!
Because if you say "Look, I'll give this six months because I love you and I don't a divorce!" then I guar-an-damn-tee you that they think you've just given them 5 months and 29 days to continue their affair, at which point they will then promise you the MOON AND THE STARS to "not do anything rash!" or some such.
It's like telling the terrorist guerrillas on what date you're gonna withdraw the troops.
A betrayed spouse who has decided to stand for their marriage for a finite period, so that their cheating spouse can see their changes and hopefully come to their senses, should ONLY say something to the cheater like "I hope you'll decide very soon, because I can't do this much longer." (or something similar)