A ninja bitch is a woman who realizes a friend is attracted to her sexually and intentionally uses that attraction to manipulate him (term originated from the intellectual whores/ladder "theory" of male/female relationships).

A girl who seems sweet and loveable and awesome when you start dating her, but turns out to be a bitch later, particularly by cheating on you.

(adjective/verb/noun/everything) like a muvvabitch, but with ninja like stealth qualities about them . or, just as a slang term for anything

Any attractive woman of asian decent

A female ninja
(Of course!)

You're now-ex girlfriend who pretended to be nice and sweet but then showed herself to be the most bitchy bitch in the world