A study came out this month suggesting 2 cups a day is all preschoolers aged 1-4 need.  Here is a link to the report  http://www.cbc.ca/m/touch/news/story/2011/06/15/milk-preschool-children.html 

My 17 month old will not drink cow's milk but she is still nursing a lot, so not the same situation as yours.  Does your daughter drink water?  My only concern would be hydration.  If she is eating other foods with calcium and fats, not drinking milk shouldn't be a problem from what I have read.