Hello,
Nevus depigmentosus can be easily differentiated from vitiligo. It is usually found at birth and size may grow in proportion to growth of the body. Nothing is to be done. If cosmetically unpleasant then laser treatment can be planned when she grows up.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
The pattern certainly fits in with nevus depigmentosus.This condition has nothing to do with vitiligo.Follow up with you doc.