Have you tried abestweb or wafo? Finch had a post on this on his blog, there just aren't too many female IM's in general due to the fact that women don't like solitary endeavors (working in IM tends to be solitary) and due to the general intelligence distribution (85% of IQ's over 140 belong to males).
I would guess that a lot of the smarter females in the industry work for organizations (google, amazon, and smaller outfits like provide commerce or marin software). They may still be interested in their own biz pursuits though