Please don't blame yourself for your actions that night. You were within your rights, and it was necessary for your self-respect as a man to react rather than to stand there and tolerate her behavior. To do nothing would have cost you far more, in ways that matter more. Believe me.
So perhaps in retrospect you didn't handle it with quite as much maturity as you would have liked. So what. That's tough to do in a situation of high emotion. And think about all the times she over-reacted, or spoke without thinking. You didn't take that as a license to go have an affair, did you? Of course not.
I look at it this way. My marriage was not perfect, and I bear my share of the responsibility for the problems we were having. But my XWH's decision to "solve the problems" by cheating is 100% on HIM. Same with your STBXWW. Whatever made this her go-to move was built into her personality long before you met her. Nothing you did triggered it, and nothing you did (or didn't do), could have prevented it. So please don't torture yourself with the what ifs. This is NOT your fault. Infidelity is strictly a personal failing, not a marital failing.
Is this bar the same one your friend wants to go to tonight? You may not be ready yet, but I think at some point you need to go there, with a good friend or two, and just have a beer. Make new memories there, and revel in the feeling of reclaiming one more corner of your world. Even if you don't care for the place and don't want to go there regularly, at least the decision will be YOUR choice, not one she made for your with her selfish behavior.
You are strong. Don't let yourself get bogged down by this.
"The secret of change is to focus all your energy not on fighting the old, but on building the new." ~ SocratesMe: Enjoying life
Him: Someone else's problem
Life shrinks or expands in proportion to one's courage. ~ Anais Nin