I think you're doing a lot of mind reading and what if'ing - spinning things around in your head trying to find the angle that's going to get her to admit the affair and then end it.
Thing is, if she admits it, she may still not end it. If she admits it to you, she may continue to deny it to everyone else. While it probably would be better if she did admit it, she doesn't look like she's going to.
I don't think you're being consistent with you actions. If you know - then act like you know. Stop being 'nice zew' and be 'dim zew' - all of the time. Stop worrying about how she can turn that around onto you.
Me:38 W:39 No Children BD: 5/13 EA/PA Confirmed: 7/13 W Moved out 12/13