My WB was the same way, and we spent lots and lots and lots of time doing transitions and getting him hot off my leg.
One game we did was to GO to a point across the ring, or to a tree in the pasture, and then halt there for a minute. Then turn around and GO back to another point. The “point to point” game really helped him understand that we were actually GOING somewhere, and once there, he could rest a minute.
Some days, the only thing we did was that game, and they were short rides because it’s HARD.
Also, think about how you start interacting with her the second you put her halter on to take her out of the field or stall. Right then, she needs to be hot off your aid to move. If she’s crooked in the aisle and you ask her to move her butt over, she has to learn to move it NOW. When you’re ready to move off the mounting block, she has to learn she walks off NOW, and walks smartly. She has to learn that every single time you ask her to move a body part, she has to reply “yes M’AM!”. It may start off with tense evasive movement, but keep at it, and it becomes energetic but thoughtful movement.
My guy took a lot to be motivated to move with that quickness. Once he understood that leg mean to move, I used the whip to emphasis not just “move”, but “move NOW”. He got an ask with leg, maybe 1 more more-insistent ask, but then he got a sharp once with the whip, and that’s what finally started getting him to understand it was just much easier to move off the first ask.
So think about every interaction, and whether you’re allowing her to react on her own terms, or yours 