I agree with Lord Helpus and many above posters. If your confidence is dwindling, send horsie off to a home she can be successfull at (dressage, broodmare, whatever) and find yourself a BTDT horse. Maybe it won't have the 10 jump and hack-winning trot, but if you can have FUN again and work on you (actual equitation and theory, maybe playing around at some derbies or Eq classes instead of just hoping to make it around a course,) that's what riding is supposed to be about. Make a "good show" the one where you move up to the 3'3 low AOs, or win an eq class becuase you did the course perfectly without stirrups, *not* just a class where you had no stops and didn't fall off.
I had a psycho mare who killed my confidence in less than a year. She'd bolt, stop, spook, or be perfect -- you just never knew which one. Like your trainer, we didn't ride in stormy weather, when there were too many riders in the ring, when etc, etc, etc. My riding suffered terribly. Finally dumped the mare for about 10% of what I paid for her, and got a darling older gelding who packed me around the low jumpers with ribbons within a year. BEST HORSE EVER. He gave me the Fun Of Riding back again.
Sell your mare, find something fun and safe, and don't look back.
A good man can make you feel sexy, strong, and able to take on the world.... oh, sorry.... that's wine...wine does that...
I don't know if I would really say this one was a confirmed "dirty stopper". IMO that's one of those that's just fine most of the time...and suddenly goes head first down to the ground slamming on the brakes at the base of a fence while dropping head and shoulders-and the rider-as they slide into the fence. When you see one on it's nose at the base with front legs splayed on either side as the rider rockets off betwee it's ears? THAT is a dirty stopper.. Somebody posted a picture a few months ago of something they were looking at buying (suspiciously underpriced) stopping at a 2' fence...on it's nose...front legs splayed...rider hitting chin on the horse's poll. Posters recommended against that one.
These keep popping up because some bright new trainer thinks they can fix it or it gets sold some distance away without sharing. Can't be fixed because rider goes head first into fence before they know what is hapening-even very, very good riders. Plus rider head versus faux stone wall never ends well, those stinkers never pick an airy vertical to stuff the rider into.
This mare sounds pretty unpleasant jumping period and not sneaking up with a stunt like that. OP bought her that way and she is that way 3 years later. Time to say uncle and find her another career as responsible owners should do.
For OP, if you are in doubt? Ask youself if you will ever trust this mare with yourself aboard? If trainer can ride it after month$ of reschooling and vet work, so what? Your horse and you need to feel safe and confident.
When opportunity knocks it's wearing overalls and looks like work.