Try using a training stick and rub her leg with it, I am thinking that if your body is in a different position she not associate her leg being touched with picking up her foot. If she does pick her foot up keep rubbing her leg until she puts it down then stop. If she backs up move with her and keep rubbing her leg until her feet stop moving. When she gets comfortable with the stick touching her and realizes she is not supposed to pick her foot up, begin to get into the bending position but don't touch her act like you dropped something then stand up, if she anticipates you and picks up her foot ignore it. Essentially your desensitizing the area around her feet, until she realizes just because your down there does not mean she needs to pick her feet up. When you brush her just keep brushing her and ignore it if she picks her foot up, but by working on desensitizing the area around her feet the problem should take of itself.
Secondly have specific cue for her to pick up her feet. I use their chestnut on their front feet, that is how I teach them to pickup their feet squeeze the chestnut until they lift a foot. When my hand settles on their chestnut they know to pick up their feet. For the back feet I apply pressure their hock and they lift their hind feet me, I pull it a bit forward then back.
Once she has a specific cue to lift her feet, and you get the area around her legs and her legs desensitized she will be able understand what you want. She is most likely just confused and has been taught bending over by her leg means pick up her foot. With a little tweaking you will be able to fix this in a short time. I can think a lot worse problems to have. Good luck.