Female heads are the worst to look for...
Here's some I've used:
-ST:TNG Tasha Yar (original 3.75" line)
-Indiana Jones Marian & Ilsa (German chick), & Irena (Russian chick). These all fit the Female Imperial Officer body pretty well.
-Mix/Match all the female heads Hasbro has done now (generic SW chicks like Rebel pilots, Imperial females, McQuarrie hero, etc.)
-Old G.I. Joe Scarlet head (not sure what line it's from but it's from some years ago and looks fairly good).
-POTC Elizabeth Swann in Chinese outfit.
That's just a few I've used Lando. There are others. GI Joes Pursuit of Cobra females are pretty decent headscuplts too, like the Baroness, Scarlet, Covergirl, etc. I've used them to make different female imperials without much modification even.
Some of those require a lot of modification though of course. Even a Vintage Leia head like Hoth Leia, could be used with the right paintjob... Look less like Leia, more like a random woman like Torryn Farr or something.