I had a gf that had a "best friend". We were going out 4 bout 16 months n d last 6 months of it was wen it really sparked up! Actually, it started with them wanting to go to the movies together (alone) wanting to see a scary movie "as friends".....hmmmmm....yeh right. Anyway, cutting down a really long and juicy story, i ended up breaking up with her and a month later, she was going out with the "best friend".
That's just my experience although afterwards i was told there's no such thing as your gf having a best friend, which couldve been useful before the relationship but eh, now i've learnt, NO SUCH THING!
I've pretty much made up my mind but still open for discusison..... is ther such a thing? i say guys, if ur gf has a male "best friend" wake up!