What would you do in this situation?

When the main care-taker of our pet Lab goes somewhere, she always asks one of my sisters to feed her her meals. Now, Sadie is very overweight so Louise (her caretaker) only gives her a cup for her meals with a little extra meat for breakfast. BUT when Rachel feeds her, she gives her meat for all her meals and she gives her 2 cups per meal. I don't like squealing, but I'm not sure what to do. I can't say anything to Rachel because she's her own person and is very stubborn. I actually feel she does it because she wants to score points with the dog. Weird but true.