I would be very unimpressed indeed. As you say, she doesn't know it exists and certainly can't ask for it so why on earth introduce it!
IMO a nursery should only be serving water or milk anyway, or fresh juice if parents are happy with that. Why on earth dish out crap that's full of chemicals when you don't have to? it's bizarre.
But do go in there and be strong about this! Squash for a SIX month old baby is just awful for a professional childcaring concern...