It's a party. Which cup do you take?

At one of our fraternity parties, one of my drunk brothers got everybody quiet and asked all the girls to either stand on the left if they were "taken" or "dating only one man" and stand on the right if they were "dating multiple men." I expected my girlfriend to stand on the left since we were committed to each other, but she stood on the right. What the hell? Then she reminded me that se was dating others when she was at her school. Oh yeah. How could I forget? Unfortunately, one of my less loyal brothers asked her for a date, and she accepted. He only did it once because of social pressure from other brothers.