I'm a horseperson...i ride competitively. as such, i work with a trainer. In my past, i rode competitive dressag and worked with a three time olympian. And here is the thing.....buck it up, learn from her, and take it as a compliment. she is teaching you--and as your skills progress, she IS going to get pickier and pickier--BECAUSE your skills are improving. she's pushing you to do your best.
now, having said that, if you aren't enjoying it, you're allowed to stop the ride and get off <grin>. I switched from dressage to western riding, because i enjoy the family atmosphere that this type of showing brings, and that dressage did not. It's not easier (heck, in a lot of ways, it's harder), but having way more fun. and oh yeah, i've brought those skills over to this sport.