I'm being a standup boyfriend about it - this issue has basically been 'haunting' me since I met my girlfriend. What made me want to open up about it is after reading this question on the site:
It's then that I realized that my girlfriend actually might be feeling insecure about how her best friend is acting toward me. You see I met them both at a collge party at the same time. They both were kinda into me, and after we all kinda hung out in a group I ended up getting both their numbers. I liked my girlfriend more cuz she had cool vibes and so she was the only one I called. This set up some kind of tension between them and competition that I don't understand because her girlfriend knows I won't sleep with her - she has tried to make moves on me drunk or the second my girl is not around. I avoid being alone with her all at all costs. She is hot, but she is shady and I know she just want the satisfaction of breaking us up so she can have power over the situation. It's pretty pathological actually.
I don't understand why women who say they are 'friends' battle each other eotionally and tear exh other down when the other is not looking, going as low as hitting on someone else's man. It's pretty digusting, So, I sat my girl down and I told her that she shouldn't bring that girl around me anymore, not for my sake, but for hers.
It's so important for women to know who their REAL friends are. A true friend would not disrespect you and compromise your romantic relationship, for any reason let alone trying to seduce your boyfriend.
Girls, take this from an ethical guy - it's hard to keep saying no when someone keeps throwing themselves at you - any red blooded guy will tell you that - so instead of testing limits - get rid of the cancer or tumor you have called a best friend and focus that attention on yourself and your man if your relationship truly matters to you. Before it's too late...