Hi J.,
I have seen this many times working in day care. One thing that I have tried and had success with is introducing a potty chair. When my oldest was the same age as your daughter and started doing the same thing, I bought her her own potty chair and kept it in the room with her at all times. When she would begin to fight about changing her diaper, I would ask her to sit for a few seconds (or minutes if you are lucky) and whether she succeeded or not, she got a reward for sitting. I started with stickers or hand stamps for sitting...and gradually as she began to start using the potty, she began to get bigger and bigger rewards. We used one m&m when she started peeing on the potty and she would get 4 or 5 if she had a BM in it (although this did not happen for a long time, we would talk about it).
Fighting diaper changes is a normal thing for children this age. They are starting to realize that they feel better with the diaper off, and it is the first step in beginning potty training. I hope this helps, even if just a little!