If she leans, then focus on getting her to take the weight off that leg, not necessarily to pick it up at that moment.
What I do is run my hand down the hock to the pastern...this gives the horse enough of a 'feel' for what I am asking; if he picks it up, fabulous, I hold it for a second or two, and release, and repeat; if he leans, I will quickly get him to simply disengage that hip. Then I will do a bit of lunging, or backing, something...this teaches the horse slowly that leaning=work, so they start "thinking" about what you are asking for. The key here is not to sit there asking for minutes for her to pick up the foot...give her the 15 seconds it takes to run your hand along the top of her rear, down to her hock and to the pastern. And if she doesn't act, then you need to just get her to unstick her feet.
My mare was the same way when I got her, and she was one that would also pick it up and give a little kick (both unacceptable); she learned really quickly that those behaviors resulted in some work, afterwhich she quickly decided that giving her feet up to me was much easier of the two.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."