T.,
My daughter went through the same thing. My pediatrician just suggested trying to suppliment the milk. Use ice cream, cheese, smoothies, yogurt (that's my daughters favorite), anythign with milk in it so they are still getting the calcium and nutrients. Yours may be a bit young for it, but I also started giving her a "big girl" cup (no lid) with just a small amount of milk at dinner time. And I would also drink a glass of milk (in a clear glass if possible) that way you can do the the "see big kids drink milk in a big boy glass". Sometimes she will drink the milk, sometimes she won't. I try not to push too hard because then they just become resistant to it. Try that and see if it works.
Good Luck