You and your boyfriend are at a mutual friend's house party. You know almost everyone, but there are a few unfamiliar faces. You're in the kitchen chatting with your girlfriends and out of the corner of your eye, you see this tall, blonde bombshell close talking with your boyfriend! You've never seen her before but they look to be quite chummy chummy. The girlfriends you're standing with are just as stunned as you are but you don't want to jump to any conclusions — for all you know she's his long-lost cousin, his best friend's new girlfriend, or his sister's roommate.
While I hope to think I would give him the benefit of the doubt, ladies, tell me, how would you handle this situation?