Should I just let go?

Dude, I do NOT think you're overreacting one bit! Only you and her can say if it's over for you, but if I were you ( and I was in a very simliar situation) I would definitely take this as a sign that if things are not over they are coming to an impending end. Basically I was in a situation with my ex in that she had feelings for one of her clmates the entire time we were together (1.5 years) but chose me, and continually lied to my face about still wanting this other person. Well I found out the hard way and ended things with her, then realized that maybe I was overreacting and tried to get her back. She then basically told me that she didn't love me anymore and wanted someone else, which just showed me how big the problems with the whole situation really were. If I were you I would take this as a huge warning sign, and suggest marriage therapy to her if you want to save your marriage. However, you sound like a nice guy and that you shouldn't put up with someone who is so very insensitive to your feelings and disrespectful of your marriage.