I have a OTTB with similar issues. Just so you know it can take a year or so to fix the charging after the fence/gait issues. Their is no quick fix in horseback riding.
Before you can expect her to slow down after a jump you need to be able to collect and extend her gaits. I would start practicing this with the walk. As well has getting her collected.
I would also do a lot of work with trot and canter poles. This will teach her not to be so excited when she sees a jump. She will probably jump the ground pole at first but after some practice she should settle down.
Another reason she might be rushing after the jump is if she is launching to the jump. Without seeing a video I don't know if she is doing this but a lot of the times OTTB without a lot of training launch and run after a fence. In order to fix this you will need to teach her to go to the base of the jump.
Let me know if you have any questions and good luck!
Wow! I never actually considered the canter poles. Yes, I will defiantly try that. Your answer really helped me. I will be working with her for a long time. Again thank you so much for your answer!!!