All these tips are amazing for picking up feet. Some I've never heard of!
Just think of it from the horses point of view(somewhat) If someone grabbed your leg and was trying to lift it what would you think? Take baby steps.
Follow any bit of the advice given cause its all great. Once she lifts her foot, hold it up for a second or two then put it down right away and praise her. Let her know your not there to harm her and that picking up her feet wont kill her.