You're not a sucker. Maybe it's just me, but your conversation seemed relatively calm and not as emotional as it could have been. Maybe your W is finally leaving the mother ship.
If she does actually end things with the OM, you need to be prepared for a whole rush of feelings on both sides. She may be mourning the loss of him whether he was a crap or not. And you will need to restrain your feelings of wanting her full attention and your major (and justified) lack of trust.
That said, I don't want to jump the gun as we don't know what will really be happening tonight. No assuming right? I just want you to be prepared. You also need to prepare for the possibility that she can't let him go.
Anyway she's recognized that she's hurt you and still loves you. That's a baby step in the right direction.