My horse is the exact same. His trot was more of a "omygodomygodimgonnadie" when I got him, and let's just say his canter is a work in progress (). Put her over lots and lots of walk and trot poles, with random halts mixed in, but never in the same place. Lots of walk/trot/halt transitions, and of course get a GOOD trainer, trust me it's worth the money. My horse now actually has BRAKES thanks to this. And yes, lots of tight circles if she starts ignoring you. Keep it interesting, change up the excercises so she doesn't get bored, and keep her guessing as to what comes next. If you can, try a cross rail small enough she can walk over it, and halt her as soon as she clears it. As she begins to calm down, throw short canter transitions in, no more than three strides. Try going from halt to trot with no walking in between, or from a dead stop to a trot. Just keep her working, and keep her attention by surprising her.