Your measurements of her KOPS and total leg length suggest she has a right femur that is longer than the left, but interestingly her tibia is longer on the left to compensate for this. This may cause her hips to rotate about the central axis of her body and may look like her hips are rocking up and down. You should observe her to see if this is the case. If so I would set the KOPS to be the average of both legs that way you minimize the effect of the femur length difference. However this rotation of her hips may be her normal riding form and if she is not having pain, then it works for her.