You could just keep brushing and move with her until she stops and stands still.
OR when she starts shifting around and being fussy feet, just start moving those feet; ie, make her work. Turning the idea of, if she wants to be antsy, then make it 'hard' for her.
In either case, I have the horse in hand, not tied. I usually never have a horse tied fast, I usually always have them ground tied, or have the lead over my arm, so I am always ready to do what is necessary to teach them to behave. I don't like to smack, or continually tell them 'whoa' or "stand"...if they want to move their feet, then either move with them until they get the idea that you aren't going to stop what you are doing, OR turn it into your idea, and make them work harder. Always do this on both sides.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."