B.R.
Wow! It sounds like your daughter is very strong willed. Nothing wrong with that, but it does make your life a little more difficult. :-) Our daughter is about the same age and at first fought the sippy cup too. We only give her formula in bottles and are trying to cut these down (she still gets bottles before bed and when she wakes up). The doc told us to start with just a tiny bit of milk in the sippy cup and then when she drank that then give a little water or juice as a "reward." Then more milk and another "reward". That seemed to work. BUT it sounds like ours responds more to "peer pressure" because she will drink milk from a sippy at day care with no question. Good luck!