I am so sorry that you are going through this! Getting a new puppy is suppose to be an exciting time, not one that makes you sad. I really hope that maybe this has been a honest mistake and that you get your refund without any problems.
As for the food on her flight back, I am surprised that she said not to feed her.
I thought that the airlines required that they access to both food and water. I just had my puppy flown to us from California to Missouri 3 days ago and she had both in her kennel. If it were me, I would give her food for the flight.
Again, I am very sorry for you and your family!!
Tammy