His friends bet he can't keep a date for longer than ten days. It's known that Bruce Wayne goes around, and his relations never last longer than a couple days; and he's eager to prove to his friends that he'll have a date for the gala at the end of the month. Someone he's been going steady with.

Your friends, however, bet that you can't break up with a guy within ten days. They knew you for your sympathy towards men, despite their various wrongdoings, and you wanted to prove that you could be cut-throat.

What a coincidence that you both just happened to be at the same bar.