Ground poles, gymnastics, lots and lots of flat work finding out her rhythm and getting her to accept the bit as well as listening to your body movements. I absolutely know what you feel because my mare absolutely loves to rush jumps and tends to take them out more often than not.
If she's raced before you're in luck cause they're usually a little calmer. Mine never raced and we put her on grain without knowing how hot it would make her. If she's skinny I recommend alfalfa hay and no grain or if you have to feed grain then only small amounts. There was a point in time where my mare was on a flatwork only training regiment. She's much better now but this is after a year of riding almost every day. It's not a week fix thing.
Gymnastics, bounces. More ground work too
Do a lot of ground poles set up in a gymnastic line. Eventually begin to put some of the poles into jumps. This will teach her not to rush them and she will learn to jump up and over them, not just "through" them.
Has she raced before? I've no experience re-training racehorses but in general its best to bring it back to basics.
Try leading her in hand over poles so she doesn't think all poles mean jumping.
Then you can try just walking and trotting into small jumps which will help both the rushing and bring her confidence up. For the rushing then you can try halt immediately afterwards and every time she pulls bring her back to halt?