You've made me think about this. Let me add this detail and ask if you feel it changes anything: the club were this happened-while it is not labeled as such- has a high patronage of the LGBT community. After some thought, I can accept that I was not entirely innocent or mature in the situation. Hooker situation? No. Swinger situation? No. Open-relationship situation is more where me and my date were. The lady in question attended the party as a single girl, made out with me, and about two or three men that night, and was seated with one of them when the incident occurred. I have a feeling he was a much more traditional type, while at the same type hoping to get lucky with the two of us. She was smart enough not to pull one of her previous male-make-out partners in front of him, but somehow thought pulling a female in would be okay...? So the conflict as I see it (and WTF, you have helped me to re-evaluate it), was that expectations were different for everyone. Me and my date had an agreement. She and I had an agreement. She changed her mind, and led her current flirtation to believe he could expect more.
Thank you for helping me to see this situation more objectively, and I mean that with absolutely no sarcasm whatsoever.
This is the first time I've ever had a negative incident occur when going out. So what I am thinking is that the venue, combination of different relationship dynamics, and mixed expectations all contributed to this fiasco. She was someone I had just met, so I shouldn't have imposed my mindset on her personal situation, or assumed that she was truthfully on the same page as me. Lesson learned.