My best friend flirts with my boyfriend

On sunday, my boyfriend, my friend, and I went bowling, then there was a guy there who likes her. So my boyfriend tried to keep him away from my friend, but he made it look like he was dating her to get the guy to go away. He was doing it as a joke, but I know she wasn't and it's really bothering me. I don't want to ditch her, she's been my best friend for years, but she is really ticking me off. And now she thinks that me and him aren't going to last very long. Which is making me more upset. So what do I do with this situation?

Ok, well you need to go ahead and let her know this is NOT cool, and she should back off, if she is a real best friend, then she will understand, anyways, good luck. :]

just bring it up and say it's kind of bothering me, you think you could back off a lil?

TELL HER STRAIGHT UP TO BACK OFF..AND TELL HER ITS REALLY TICKING you OFF AND IF SHE WAS A TRUE BEST FRIEND SHE WULDNT HAVE DONE THAT IN THA FIRST PLACE ...

Flirting is almost nothing, but you may tell your best friend that, you are the first, and she can be only the second. But a girl, and her best friend, and the girl's b/f can form a nice company, beleive me.

beat her a*s sorry but dats what id do