I appreciate that response. You may never understand her mindset. Most men can't understand women, period, much less something like this.
What concerns me is how afraid you are to leave, even on a temp bases. If the EA moves to PA, I am worried that you will continue to find some excuse that allows you to stay with her. A lot of men have stated how knowing about an A would be better than not knowing......until it actually happens. They think they would drop the WW like a hot potato if she's cheated. Then they discover they can't bring themselves to do it.
Like I said previously, you do what you want to do. I just think this goes deeper than you seem to realize. If you decide to linger on, I believe you need to brace yourself for more to come. The way I see it, she is not going to stop this A without you taking action.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!