Ha ha, my 10 year old Hannoverian gelding is doing exactly the same thing, except at 4th level. He’s a very opinionated princess who prefers to play Christian Grey versus Ana, if you get my drift - “submission” is not naturally in his vocabulary. Dressage has been very easy for him and he gets very offended when something actually requires hard work, like canter pirouettes. What we’ve started doing is working him in hand with side reins. My trainer is basically beginning to teach him piaffe in hand so he understands that stopping and kicking out is not the appropriate response to hard work - you must MOVE YOUR LEGS in response to pressure, not throw a temper tantrum and kick like a human toddler. I’m not talented enough to do what she does but now that he knows the deal, if he starts it with me under saddle I can get off, lunge him in side reins for 5 minutes and then he’s perfect. He’s a big guy and unfortunately he learned that his 5’2" mother really can’t kick or hit him hard enough to make him care. That said, I have had him his whole life and this is pretty much the way he has always been personality-wise. If this is something new for your mare, I would second eveyone above who suggest looking for pain-related reasons first.
It’s been seven years, hopefully she’s gotten it going by now.
oops did realize it was such an old thread, sure hope it is all resolved by now (:
Hah me neither - would be interesting to hear 
I searched the OP’s posts and it turns out the horse had EPM. I had one with EPM that exhibited the same symptoms at first. People said, “He’s a brat! He’s a jerk! Beat him until he goes forward!” Poor horse was just doing the best he could with his diseased body.
I urge people to test for EPM when this kind of behavior surfaces. These poor horses simply can’t do what you want, and all the training, beating, long lining, longeing, chiropractic, etc. won’t help.
I searched the OP’s posts and it turns out the horse had EPM. I had one with EPM that exhibited the same symptoms at first. People said, “He’s a brat! He’s a jerk! Beat him until he goes forward!” Poor horse was just doing the best he could with his diseased body.
I urge people to test for EPM when this kind of behavior surfaces. These poor horses simply can’t do what you want, and all the training, beating, long lining, longeing, chiropractic, etc. won’t help.
Poor horse, tHANKS for update. Young horse lame on both hinds with no reason found yet people here were sure the subsequent problems were behavioraL. 
She just had her hocks injected as she was lame on both hinds, but has been back to work for at least a month now with no problems.
