If she absolutely will NOT get off your leg, you have a training problem and you need to go back to slow to fix it.
I would take her to the middle of the ring and flex her left and right to loosen her up, then work on really getting her to move off your leg. Sidepass, forehand turn, haunch turn, do whatever you can to gain control of her body parts. Do some circles to get the arc back in her body. Do some counter arc circles too, with her nose tipped to the outside of a circle and moving the shoulders around.
After you can do this comfortabley and she is loosened up, THEN take her back to where you are having problems and try and fix it.
If, after all of that work, she still does not listen to you then get physical with her. Grab her nose with one hand, get the flexion, and use your calves to drive her up into the bridle with your inside leg getting her a point to round herself to. Make sure you are sitting even and not leaning to any one side of the saddle.If she dives in, move your weight to your outside. If she dives out, move some weight to the inside seatbone. Just don't be leaning out of the saddle. Remember there is a difference between shifting your weight and leaning out of unbalance.
On that note, do you have a trainer to help you?
Pssh.I didn't pick up the wrong lead
It's called a counter canter...
...A very advanced maneuver.