Is your boyfriend actually doing anything wrong? Or is it all this girl's doing? Is it harmless flirting? Or is it serious macking on your man flirting? There are a lot of little factors that are just as important in finding out what's going down here.

Either way, you're going to need to have a face-to-face chat with somebody. If you're boyfriend is an active participant in all of the flirtatiousness, then he needs to own up to it. Let him know that it makes you uncomfortable. If he's a good BF worth keeping around and there's really nothing suspicious happening behind your back, then he'll understand without making a fuss.

On the other hand, if he's not the real problem, and instead it's simply this chick getting involved where she doesn't belong, then you've gotta' go right to the source. Pull her aside next time you see her and let her know that you have no problem with her being friends with your boy, but you'd really appreciate it if she'd step back a bit with the flirting.