Get a vet to check her and make sure your tack fits her properly. If everything is fine and she’s doing it just because she’s being difficult and she is unwilling to do it, tell her off when she does something you do not want her to do, and reward her when she does the thing that you want her to do and when she is behaving. Hope this helps! 😀
Have your vet check her teeth.
Check your tack, horses continue to grow, a saddle may fit them for a bit but as they gain muscle it can become ill fitting.
If all that checks out ok. Go back to ground work.
Have u changed your tack or what u use for her? Has she recently been to the vet or had a dentist appointment? There is most likely something that is causing her pain which is why she is reacting like that. Do u use spurs? If so those might be the problem.