I am not a western rider, so I don't have much advise about that but I would be concerned that she is so young and has little interest in working.
If I were her owner I would stop doing that type of work entirely and make riding fun again for her. Take her out on trail rides, or with another horse and rider for a good gallop. Once she is enjoying herself again, I would slowly reintroduce the work you want her to be doing. And finally I would ditch the trainer who has been working her.