Taking turns...

A reader writes... I’ve been dating my boyfriend now for a little over a year and we have a stable and trusting relationship. A few months ago one of his closest friends broke up with his girlfriend. Recently my boyfriend decided to hook his friend up with a girl he used to sleep with. My boyfriend was never in a relationship with the girl, it was just “casual sex.” The problem is that his friend and this girl are starting to get serious and are on the verge of an exclusive relationship. The possibility of going on a double date with these two is causing problems for me. I don’t want to hang out with someone my boyfriend used to sleep with! Also, how can I respect his friend? He basically took sloppy seconds. Or for the girl? She allowed herself to be passed along! How should I handle this?