I've done this too, though I only realized it when I consciously wrote a YA short story about female friendship. (For the Bordertown antho. Because if you're going to Bordertown, of course you have to take your best friend with you, right?) My middle grade books have strong female friendships, but while my YAs have strong female relationships across generations (and I do think that's a hugely important bond as well), there's not so much going on within a given generation. I'm still thinking about that.
Anyway, Mette and Sherwood have already done this, but I thought I'd ask here, too: what are your favorite female friendships in fantasy? What books would you consider must-reads for a discussion of same?