How about some cartoon villainesses?
Geek that I am, all of these pictures are from the Batman universe.
Inque from Batman Beyond
DeeDee from Batman Beyond (costume for two people)
Here’s a better shot of her costume:
Harley Quinn from Batman
This shot better shows Harley’s personality:
Poison Ivy from Batman
Cat Woman from Batman
I thought about putting Wonder Woman and Bat Girl, etc. but you don’t want to be a good girl on Halloween, right?