How would you feel if you’ve been taking to/casually dating someone and they start flirting with someone else while drunk?

[roxystars19]

Friend of mine has been talking to this guy and she found out that while he was at a friends house, he began flirting with some girl. He was drunk at the time and the two of them (he and random girl) haven’t spoken since that night.
Technically, my friend and him aren’t dating, so he isn’t “cheating” on her. But I say otherwise.

[20yearsolder]

How would I feel, Well if I had feelings for him I would feel hurt but with that being said there's no exclusivity contract between the two so not only is he free to do whatever he wants, so is she