This is the way I would train a girl.
First I would tell her that she needs to work on her lower body (whether or not it's true is irrelevant). Then I would send her to do some stiff legged deadlifts but being the gentleman that I am, I would make sure her form was right. After all, safety first.
I would cup her ass into my lap to maintain stability and my magic wand (it's my own personal tool to indicate if form is right....if the wand gets a big strong signal, good form. If the signal is weak and small, bad form) would know what is up.
Best of luck in your endeavor.