My first horse came to me difficult to bridle, would throw up his head and pull back quite violently. I used a method I found online (https://www.youtube.com/watch?v=GCYdXwgZKo4
) and I just took it real slow, real patient, but persistent. I made progress immediately, the first session I stopped when I could hold the bridle against his face without head tossing. Session two I stopped when I could hold the bit against his lips with him remaining calm. Session three I was taking the bridle on and off. I feel this is an EXCELLENT method for if the horse has actual misgivings and thinks
it's going to hurt him/her.
I just had his teeth done to rule that out, and today when I went to put on his bridle, he had regressed, being much more evasive than he has been (and I don't blame him, as the last thing he had put in his mouth was the gag for the dentist) and I went back to the method I used last time, but it didn't seem to be working, and I was pretty sure he was just seeing what he could get away with, so every time he "won" with his little evasive tactics, I sent him off (we were in a roundyard) and made him work for a bit. After the third time that I sent him off and then when he was listening to me asked him to "whoa". He did an excellent stop straight away which is another victory for us yay! So I went over and gave him a rub, walked back over to the bridle, he followed me, and a put it on without any argument. In this instance, I knew that he was seeing what he could get away with and that's why I used more pressure and it worked.
But definitely rule out pain/teeth issues first and be sensitive to begin with, especially if you think she's responding that way because of previous bad experiences, you want her to be able to trust you, not frighten her further. Good luck :)