This is going to sound strange, but do it with her! Get off, take her to the jump she's scared of and jump it with her so she knows to trust you that's it's okay
Make sure you always keep your leg on. Horses can sense feeling so don't act or make it seem like its a big deal. Let her look at all the jumps before mounting. But the main thing is to keep your leg on and help her do her job. The more you jump around the more and more she will get used to it.
In addition to the other answers, walk her over the jumps to get her used to them.
Use guide poles to show her the way over the jumps and give lots of praise
Start basic and low jumps, the continuously build how "spooky" or decorated a jump is and the height when you feel that both you and your horse can safely and nicely make it over