Hi,
Based on your post, I think it would also help if the parents will be educated or made understood of their child's situation. As a child, she may not really be aware of her situation. Since her parents are the ones who take care of her, they should do the necessary changes for her first even just with the food she eats... When the time comes that she has understood things about being obese and about weight loss procedures, then maybe she can undergo the surgery.