Are you your best friend's best friend?

I am, she is, we are! LOL
I've known my best friend for donkey's years. Couldn't really stand her when I first met her and vice versa, but we worked it out and she has been my heart, my rock and my refuge for more years than I care to think about. I hope only, that one day I can return to her the love and devotion she has given to me. I don't really like her husband and she's not crazy about mine, but she is one of those rare people that never lets other people opinions change hers when it come to me, and I'm the same with her.
We've been through the 'wars' that only life can send your way, together and survived and come out the other side better people. I can't imagine her NOT being my best friend.

I don't think that I am my best friend's best friend. It does not really matter to me at all. I could be wrong about this. I have never asked her and probably never would ask her. She has a really close friend that she has known for most of her life and I just assume she is her best friend.