I would take a long whip (if they don't frighten her) and tickle her leg with it while standing at a safe distance of she takes it and doesn't make a treating move at all give her a treat, if she does move then pup the whip away and try again. I would try to think of something like a punispunishment such as a small jerk on her lead or such if she does threaten to kick
Understand what she likes most (treats, pets, a nibble of grain). When she stands for you after having touched one leg for a few moments, treat her accordingly. Once she gets used to this, try to have her stand while you touch one, then another leg, then treat. After a while, she will associate you touching her legs as the precursor to her most favorite thing!
^^^desensitizing will help a whole lot!! Just don't stop when she freaks out because that is giving the release of pressure at the wrong time. ( she will think that the reaction she gave you was correct. ) and try your best not to "tip toe" around her. She will most likely look at you as a predator. ( horses are prey animal ) just walk normal around her ect.