Rob,
Sorry your XW is such a whack job. Wow, what kind of person would deny a 5 year old a trip to her grandparents for Xmas? Knowing your parents have paid for the flight, how could she??? She is very lucky, you don't say,that there is nothing in writing about a "noon" drop off. You were so smart to elude to the fact there are no emails or texts about it, in your reply. She just so needs to get the idea that if she is not going to be reasonable, she will maybe haven to adhere to exactly what is legal. If she insists on the time maybe you could pay the fee to change to a later flight, it would be such a shame for your parents to lose the money and also not have G on the holiday.