There are actually LOTS of bands with female instrumentalists. A few are all female, but most are mixed. As I posted on another thread, MOST of the small-venue indie bands I see are mixed these days, which is just not reflected in what gets media airplay, where women seem to be stereotyped as either solo vocalists or members of all girl "manufactured" vocal ensembles who don't play instruments.

On the Indie scene, Ipso Facto, fronted by Rosalie Cunningham, were a great, but short-lived all female band. Vicky Smith, their former drummer, is really good.

Tiny Tin Lady are now 5/6 female, though their horn player (!) is nominally given a female stage designation.

At the last small venue indie mini-festival I went to, at least 30% of the band members (about 25 bands) were women, playing everything from keyboards, fiddle, lead guitar, flute, bass, drums to sax and trumpet.

They're there, but seem to be "filtered out" during the climb to mainstream acceptance.