Originally Posted by Stichy
Also, when she's in the feild, her left side is pefectly fine. Could it still be pain?
She may have learned to compensate for a soreness or injury out in the field, turning left in a very particular way that doesn't hurt too much. But with tack and/or a rider can make it so she's can't compensate as easily.
I would vet a chiro/vet out asap.