Some characters like the "nobushi", for instance, were typically females using the naginata or ko-naginata. It kinda goes with Ubi trying to tie some of the actual history into the game. That weapon was a great weapon for the women because of it's capabiliy to keep enemies at a distance.
Valkyrie was pretty much the same for the Vikings. Valkyrie is a female spirit in Norse mythology.
PeaceKeeper, I can't give you any historical facts on. She is mainly speculation from different types of warriors. I know the Scottish had a fighting style of sword and dagger but not locked into the female aspect. It would seem she was created for fun more than a historical background.