text: I am CERTAIN that you are smart enough to figure this out.  If she is your BEST friend then this should not even be a question!  IF she is your best friend, then you respect her enough to back off and get your own life and your own boyfriend.  Remember that boyfriends come and go, but friends should be there forever.. when all else fails and the boyfriends have hurt you badly, the best friend will be there to hold your hand and cry with you.  Think VERY hard before you allow a guy to mess up a great friendship.. it really is NOT worth it because if you think about it.. if this guy is so great, why is he flirting with YOU while he is HER boyfriend????  I wouldn't want any part of that jerk.