I have tried circling her smaller and letting the circle slow her down... goodness I have never ridden a horse that can speed through a 5m circle like that little devil. Sometimes it works, but as soon as I ask her back on a larger circle and she loses her tempo, she's back to buzzing around the ring.
Half-halting is not working at the moment. She needs to learn to accept my rein pressure before that happens correctly. At present she just pops her nose up in the air and actually runs blind.
Checking and giving is no avail either... it seems that the more rein is there, the more she rushes - almost like she's been trained like a thoroghbred that bit pressure = fast.
Other than the canter, her training has come really far, and I couldn't be happier...
I am up for any new ideas.