Can the term "jack/jerk off" be used for female masturbation?
I'm not sure how widespread it is but jill off (a reference to Jack and Jill) is sometimes used.
You should use "frigging", "frig", "frig yourself", or "frig off" (although this has a different meaning too, similar to "fuck off", but not as rude). The vulgar usage refers to female masturbation, but the dictionaries seem to have looser definitions. This is the term used universally in translations of the Marquis de Sade to English.