You are dramatically overreacting. First, you guys chose to go out to a club for your first "for real" outing. I'm not sure what this means, but I assume you're trying to say that this was your first formal date? Maybe next time chose a more intimate place to foster positive thoughts and feelings. Clubs are loud and crowded.

Second, yeah she took some selfies with a guy, but so? I can imagine the scene of you being so obscenely uncomfortable that your eyes had lazers shooting out of them. That is very passive aggressive. What are your future expectations for her going to be in the future? Those need to be set so she can decide if she wants to be with someone who wont let her take selfies with randos at the club. It's immature, but I don't consider that cheating.

Third, you left her at the restroom. Alone. Omg. You left her unsupervised. She could have taken a lot of selfies when you weren't around, OR she could have needed you around when you promised.

You sound super insecure.