Flirty golddiggers who lie about being golddiggers.
Men who fake being nice in dating typically do it to get sex so they can satiate their ego. Women who fake being nice typically do it to exploit another person's status and/or assets so they can satiate their ego.
A lot of the "nice girls" have an entitled princess complex with the belief they always "deserve better" (ego), even when they refuse to do what's typically expected to earn those luxuries. They see themselves as unique and automatically deserving of special treatment despite not having any significant attractive qualities to begin with (ie: basic flabby plain chick with no impressive merits who demands nothing less then a sensational hardworking man who's the perfect package). This is similar to how "nice guys" feel entitled to sex for simply demonstrating bare minimum courtesy without making themselves a better catch and obsessing over getting the popular hot chicks as "alpha" status symbols.
FYI, the female counterpart to the popularized alpha male concept is "queen bee".
