I have a hot TB and run into the same issues.
What discipline do you ride? We've started training in dressage, and that has done wonders for our riding partnership :)
I do a lot of walk-trot and trot-walk transitions. Also, I'll ask my horse to walk on a loose rein, and if he breaks into the trot, rather than pulling on him, I'll have him collect. Once he's collected, I'll ask him to walk with my seat but keep him on the bit. When he walks, I'll let the rein back out. It's a lot of repetition, but he's better, haha.
Also, I make sure not to pull on or hold his face. As part of our dressage training, I expect him not to pull on me, and I won't pull on him (or at least that's the goal, haha). A biggie with him, and I've found most of the hot horses I've worked with, is that steady pressure like that will make them push forward against it.
Another thought that comes to mind, what kind of bit do you have? Could she be reacting against a harsher bit? Arabians and TBs both tend to be sensitive. I ride mine in a thick D-ring snaffle; I don't worry about having brakes in the arena.
Also, could she be bored? My TB is actually hotter when working on dressage or jumping than when trail riding, and he likes variety, so we never work on one thing for too long. Arabians are really smart and tend to get bored easily; they're like the Border Collies of the horse world, lol.
Hope some of that was helpful :) I love hot horses; they have so much energy that you can direct any way you want once you have established communication!