Retaliation or fair?

Last year, my mother-in-law asked us Saturday morning to look after her dog for two weeks starting right then. We said no because we had a four month old at the time and the dog was not good around her (jumping on her, pawing at her, and knocking over her play pen when she was NOT in it thankfully!). The dog is not allowed around our daughter because she's too rough.

Our power is out and I asked her if we could store my extra breast milk in her freezer, otherwise I'm losing about 100 oz. She said no, and then said something about how when she needed something I said no.

My husband says that we asked her and she said no and it's her prerogative. It just sucks. I believe though that the two things are so vastly different that you can't say it's just one person helping out another. Watching a poorly behaved dog for two weeks with no notice is very different from storing breast milk in a freezer.