I know, LfL, and that's what I'm struggling with, too. As NOP says, "only you can decide how much disrespect you want to put up with," and what I'm waiting for is something CONCRETE with which to ask her to leave, if it comes to that.
She no longer denies the romantic attachment to OM to me. She does, however, still tell her parents that "he's just a friend." Our daughters know the truth, W knows they know the truth, and so they just never bring it up.
Her stated desire is to get our financial ducks in a row and then try to forge an amicable, uncontested divorce. If the affair is still going on, however, and I can prove it, there will hardly be anything "uncontested" about it, I will reveal to her the type of evidence that I have (but not how I got it), and I will kindly ask her to leave, NOW, and let her know that if she fights me for custody, or if she tries to stick it to me alimony-wise, she will have a battle on her hands.