If you'd seen Michael Jackson's previous female guitarist
Jennifer Batten - played with Jeff Beck too. She also taught at GIT and had a regular column in Guitar player at one point - monster player.
Also: Kaki King, Lani Stern, Bonnie Raitt, Liona Boyd, Sharon Isbin, Susan Tedeschi, Nancy Wilson, Ani DeFranco. Locally, Jane Mayne and Edi Niederlander spring immediately to mind.
But I think KayDUB was asking: why aren't there more
female guitarists (not Girls KD, not girls) and why aren't there any
female guitar heroes
? For a great article on this very question, try this link: http://www.washingtonpost.com/wp-dyn/articles/A19175-2004Aug20.html