Not taking a full bottle with MIL

Melanie
So my daughter is champ at taking a bottle except from my MIL. For some reason she only drinks a few ounces then stops and later wants more. Well breastmilk is only good for a certain amount of time after it's been thawed and warmed so she sometimes ends up wasting some!!!! She doesn't do this with anyone else. How do I tell my mil how to give her a bottle? I feel stupid because she obviously knows what to do she raised three kids but I just hate seeing my milk go to waste and to have the baby's feedings off schedule especially since I'm about to back to work 😕