So then work on making sure it's not coming from a place of selfishness.
Look, I'm not opposed to you doing things, but I'd prefer to see YOU lead with it, and PROACTIVELY decide to do something that you think would speak to her LL, if that's the way you want to go. Again, personally, I have never seen someone "win them over" back to a marriage when the other person is actively involved in an affair, but if you are going to do it, just do it proactively.
But I mainly brought it up because you seemed to indicate that you:
a) couldn't afford it;
b) had other higher priorities; and
c) didn't seem to be content with your decision.
I will admit that it's far more difficult to figure out what your DBing style should be when your past history has been one of legitimate "controlling" behavior. (I emphasize "legitimate" because "YOU ARE CONTROLLING!" is often gaslighting b.s. on the part of a wayward spouse, and really means more like "I resent you not letting me conduct my affair, unencumbered!") If your past style has been overly pleasing/accommodating/supplicating/"Mr. Nice Guy" then this is a far easier decision: do the "180" that would be represented by taking a strong stand.
However, if your past interpersonal style with her HAS truly been domineering, controlling, dismissive, etc., than you do have to figure out ways to show her that other side of you, while not being a doormat. I would still maintain that she's going to be largely blocked to any attempt to receive that, as long as she's in another relationship, but if nothing else you still have to do it because ... guess what ... it's The Right Thing to Do."
