We had a similar problem with our mare years ago. When we started riding her on a regular basis, she began fighting with you and would rear when you ask her to do something. Like you, we looked her over from head to toe. I decided we would float her teeth. When we got in there her teeth were sharp but we also notice that she had both upper wolft teeth. They both had lots of extra gum tissue around them and they were extremely sharp. Once we pulled them and gave her a few days off for it to heal, we started riding her again and she has never reared since.

Mares, I have found often get over looked. In boys they normally get pulled when we knock them out to castrate them. Since fillies don't need anything done with them we tend to forget to check them. It is recommended to float a horse for the first time at 2 years just before they go into training and at that time the wolf teeth can be removed. Young horses will almost need done yearly until they are 5 years when they will have their full set of adult teeth in. Normally after age 5 you can go every other year. Unless the horse has a dental condition like a miss alignment of some sort. Dental care has come a long way in the past few years with all the power tools that are now available. THey do a better job, and are easier on the horse and humans.

Hope this helps.