Engaged sorority sister acting as though she is single at the bar

While it would be ideal to out this girl to her guy, I think it'd be extremely cruel to do so (in the ways our lovely GC males are suggesting) considering SHE'S HER FREAKING SORORITY SISTER!

Would you treat your own brother that way? I don't know, I just think that if I was the hookerish engaged girl in question I'd want it so that the situation was handled in a more discreet and less tacky way.

But that's just me.