I have a Thoroughbred mare who is an ex-racer and stuff. She is really good, and I use her for jumping and western. When I go over jumps we set up, I start at a trot and we're rather fine with it. She normally listens and manages to do what I ask. Though, as soon as I ask a canter, she starts off easy, and at the pace that I want her to be at, but as soon as she comes up about 4 strides from the jump, she speeds up and over jumps it. When she's on the other side, she doesn't listen and I have to circle her to get her focus back on me. What I've been doing is after the other side, I pull her back, turn her to face the jump and make her walk over it several times and slowly build back up to a canter to make her stay slow. It tends to work for the most part, but she does it again, and I have to repeat. I'm not sure if what I'm doing is right, or if there is another thing I should be doing to slow her down.
This year I plan to do jumping shows with her, but I'm not sure if I should right now because of the fact she speeds up and stops listening as soon as she does instead of staying collected. Is there a way that I can work on getting her to slow down, and keep her listening to me after the jump?