Does she flex laterally and vertically?
If so, I would take p bit contact, gently touch her mouth and ask her to soften her chin, squeezing with your legs to draw her hind end underneath her and draw her head down. This round her back and activates the hind end.
If she does not flex, start by teaching her to yield to your hand pressure from side to side with one hand until she will give her nose. Then use that to draw her head down vertically from the contact with both hands.
Pssh.I didn't pick up the wrong lead
It's called a counter canter...
...A very advanced maneuver.