I have a 5 year old Arab mare too! She does the same thing! I just need to always be doing circle patterns etc to keep her concentrated on what she doing next:) and jumps in a row get my mare a bit excited:)
Set up a few jumps and try just hand walking her around them, let her smell them, once she's calmed down get on and just walk or trot her around without actually going over them. You could try poles and work up to the jumps too
Try trotting over some small jumps then work your way up keeping her calm.
Longer warmups are good, maybe lunge for 5 mins before you jump
Grids, circling before the jump, and different exercises may help. Also putting bounce poles before mat help her slow down. Just try different ideas and find out what works for you. Try to not always do the same grid or exercise, as she mad get bored and start to act up.
Use the in and out exercise ! Put a ground pole before and after the jump, they have to slow and correct their stride in order to jump this. Put one ground pole ten steps (or however long a half a stride would be for your horse) before and after jump! Helped with a little hot red head Arab I leased !
Lay a few ground poles out before the jump so she has to think about the poles more than the jump. 💜
Work with grids and ground poles.