some people put plastic bags in the box so that they get used to the noises and then don't get scared wih other things
I agree with Sarah, keep doing them until she's used to it. Put wheelbarrows upright next to a jump to resemble wings, flower baskets, towels, buckets etc under jumps as fillers, and go to a lot of practise shows on different grounds if possible. Good luck!
I've had exactly the same problem, just practice practice practice. When jumping at home try to jump with fillers she hasn't seen before, if you don't have them try putting things on top/underneath of the jumps you think she would spook at so she can get used to jumping the scary monsters!
Also leaving things such as flower baskets, fillers etc in the arena when we were doing flatwork training helped with my horse so he got used to seeing them.
Show her the course prior to jumping and train with fillers 👍 hope this helps x
Get off and walk to it
Give her treat if she allows it closer
let her touch and smell it.