Stop/ backup several steps and stand. If her feet move without me asking, we back up a few more steps. This made her very sour to backing up. :(
Stop and one-rein for any uninvited steps. I felt I was going to wear out the effectiveness of the one-rein though after several days with little/no progress.
Stop and tight circle with whatever foot she steps out with. Not encouraging any motion, just telling her "Look, if you want to move your feet, it will be in a boring circle" until she decides standing is better then getting dizzy. After several minutes of circles at each stop attempt, she will stand for a few seconds. But no progress as to shortening the time we spend circling or achieving stops without having to do this.
I try to stay ahead of her movement; like as soon as her feet are still, I ask her to move out before she does it herself.
We've been at this for several weeks. She rides with full cheek french link bit if that helps any. She is VERY light-mouthed to everything else; she steers with a squeeze of your pinkies. Suggestions welcome, even if it's just "stick with it longer!!"..... thanks.