We went to an event about 60 people, some I knew. At our table was a young woman who caught his attention and it seemed that she was fighting off the urged to succumb to his attention, maybe because I was there. He 45, me 40, she 28
Around 12 I was fed up and wanted to go, he had had too much to drink and wanted to hang around, drink water and sober up. I saw that as an excuse to sound more time chatting up the new person. I decided to leave. (Towards the end of the evening, he was catering to her more than to me, pouring her glass, ordering bottled water for her etc...) I asked him if he'd be open to staying to sober up even if I left to which he said yes.
I was hurt but left the event saying good bye to everyone and him included. I am glad to have seen what I saw so:
As someone's date, what're your obligations to that person?
Unspoken obligations notwithstanding, if I were in your shoes, I would have given the girl a wink and said, "All yours, Sister."