Re: What do I say?
Our diaper bag has an insulated compartment for bottles. Maybe yours does, too? It could keep the bottle cool until your mother wants to use it.
There was one occasion when we were taking a long road trip and we decided to feed the baby in the car, so to warm up the milk (from the cooler) I held it between my thighs for a few minutes to take the chill off. If your daughter isn't too picky about temperature this might work.
BTW, when I first read the post I saw 23.5 and assumed months, so I was thinking "why does a nearly 2 year old need a bottle mid-day?!?" but then I snapped out of stupid mode and read it correctly.
My little man was born 12/17/2010.
Baby girl was born 4/30/2014.