Flat work, lunging, learning your distances and using a ground pole before the jump
Talk to her and say woah and try holding her back so she adds a stride instead of leaving one out
Definitely work with poles and gymnastics also try challenging her up to the base gymnastics will definitely help!
Use ground poles before the jump to mark the take off point, they should be set at about an equal distance to the jump's height. When riding up to a fence, you can also sit deeper in your seat and ride her right up to the jump instead of going into two point and letting her find her distance, hopefull this helped and good luck!
This will help both your eye and will teach your horse to wait.
You can work on many different pile exercises with
lines or bending lines or just simply cantering over a pole and really work on her balancing and waiting. You can do circles over a pole or a figure eight to make it fun for both of you. Eventually you can start doing circles incorporating a small jump and then work on bending lines and lines with small jumps. Have fun!