Before we can think about strengthening the horse, we need to achieve a calm state of mind. To me, an anxious athlete is a travesty- we have a responsibility to the horse to help them achieve a calm, but engaged place in their mind.
After that, we need to teach the horse to get positioned. I often relate this to a person in the gym headed to pick up the heavy weights- before you can safely squat them, you need to have a handle on your own alignment, and position yourself correctly. Only then can you begin to develop strength. And strength only happens correctly in relation to the body’s ability to stay in position- strengthening without good alignment will always put the body at risk.
This horse is learning to be calm, and get positioned. Nothing fancy, but work that will benefit her body far more than repetitive strengthening exercises at this stage.