She will tend to catch edges when running straight on cat tracks, and her skis will behave erratically in a turn. A more serious effect of this biomechanical structural difference is the increased probability of knee injury. Orthotics can also reduce some stress to the knee. After properly stabilizing the foot, canting can be addressed. Cants have long been used to correct leg alignment.
Cants are simply a mechanical means used to level someone s body.
You can think of it as putting matchbooks under a tippy table. Those installed between the skis and bindings are generally more effective than cants integrated in the boot. The need for cants is a biomechanical fact, not a crutch. When she skis she must shift her pelvis more in order to keep her center of gravity over her weight bearing foot. As a result, there is greater hip movement.