Hi,
I went through the same struggle with my daughter (at 10 months, but the same nonetheless). One thing I learned is that once your daughter's at the age she is, she only needs 16oz of milk a day. Feed cheese and yogurt, things of that nature to make up the difference.
With our daughter we found that warming up some milk, not a lot, just enough to take the chill off of it, and giving it to her when she hops out of bed in the morning, works wonders. She drinks the whole cup down and that's fills her milk requirement for the day. The rest of the day she drinks water. Makes traveling during the day easier as well if I know she only needs to have water and not a drink that needs to be kept cold.
Have you tried a straw? Sometimes that can be fun, or try leaving the valve out of the sippy until she gets the idea, just make sure you supervise as it can leak or overwhelm her with the volume of fluid arriving all at once.
Mostly, realize that it takes time and yes, she will decide to drink. I went cold turkey with my daughter. We tried to go gradually but never really made much process so one morning I put everything in storage before she got up and that was that. She was upset the first day, but I could honestly tell her and show her that at home, there was no other option. By day two she decided that she could deal and life went on with no major disasters.
Good luck and remember you are already a great mom for seeking the advice of others!
Kate <><