E.R.
Here is a link to nutrition for children. It covers a lot of topics!
http://pediatrics.about.com/od/nutrition/Nutrition_for_Ch...
Under 2 they only need 500 mg. If you look at the nutritional info on the jug of milk it goes off of an adult. We require 1000mg so if 1 cup is 30% that equals 300 mg.
When she gets a little older you could compromise and say if you drink this cup of water then you can have a cup of milk. That is what I do with my daycare kids in order for them to get enough water throughout the day. =)