Start slow and low. If you have eliminated the possibility of physical pain, start with ground poles, move to small cross rails, and so on. Make sure she is absolutely confident with the level you are practicing prior to increasing the height.
Patience. Go back to basics. Poles poles and poles. Get her used to standing over poles and from there, w/t/c over poles. Then cavalettis. Free lunge her over a single fence. Does she go to it or need encouragement. Horses afraid to jump are usually scared from a bad experience that caused them pain. Eliminate back , dental and vision issues prior to starting any jumping work.
I read this in a heartland book a while ago, join up with him and just help her get her confidence back . Maybe spend some time on the ground. Once your joined up , walk over a little cross rail, she will follow you over. Start small. It's great your staying with her!
Confidence will be a big issue. If you can, I would trot or even walk over some small jumps maybe cross rails and work up from there. If she is too worried for that then I would lead her over them in a halter and longe line. The biggest key is you have to move slowly. It will take some time, but she will come around
Start small and slowly get her confidence back 🐴
Constant reassurance and start with poles on the ground and raise them in teeny increments. Immediately reward her if she hops over the little ones. She just needs to get her confidence back, poor girl😞 Seeing another horse jump might help her as well. And to clarify, have her on a lunge line when you're helping her jump again.