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.
Or, if OM1 dumps her (and it does seem to be about a 25/75 "unrequited love" situation with those two, so that's a fairly real possibility) then I'd put the odds at about 90% that she would actively seek an OM2 to get another fix of that rush that she enjoyed from OM1.
