Both of our Ottb buck ALOT we have a lot of benefit of doubt and ride through any bucking as it’s usually a baby thing of being bored, excited or just being a Tb behaviours. We always asked for them to go forward and use there back end for that instead of bucking - both have since grown out of it.
I have an ottb and he does the exact same thing if you’ve ever heard of the “one rein stop” or “hurricane” every time your horse does something you didn’t ask it to do or that isn’t acceptable like doing bunny hops and bucking do the one rein stop and hold it there until your horses feet stop moving then once it has stopped start again if the transition from stop to walk this perfect and listens well then move to walk to trot if that seems perfect and no issues then move to trot to canter transitions often if they’re having issues with trot to canter transitions they’re having issues with the others too it’s just harder to see because it’s seen as a simpler task
Bend her around your leg to "take her rear away" and when she settles push her forward. If they have the energy to buck they need to work a little harder, and circles are harder than straight lines. The smaller the circle the more challenging for the horse. They either quit the sassyness and watch their feet or they get into trouble
i had an OTTB that was the same way... usually i had to do a small circle to make sure that all attention is on me, then ask for the canter
Did you have her teeth checked? They should be floated once or twice a year.
Really get her bending in the corner so she is focused
Canter on a circle and before you ask for canter you can do some more working trot to tlget her a bit more tired, you can add some pole work to get her focused.
Also have a look if you are feeding her some too much energy in her feed.
Also she might have some pains so if none of this works u might wanna speak to your vet