How do I get my horse to stop rushing into fences?

I normally ride western and speed, but I also like to do hunter hack and just for fun jumping. For a while she was okay with jumping, and now she bites the bit and gallops as soon as she knows thats what I want her to do. Its not scary or anything, but afraid she is going to hurt herself and im never going to be placed in a cl again. How do I get her to take her time and jump slowly and steadily?