Horse behind the vertical

How good that you are looking at the whole picture to help your horse!

Here are some tips for an exercise you can do ridden and from the ground.

From the ground:

Work in a headcollar and on a line. Lunge the horse in different ways around four poles laid out as a square on the circle line, see the image. Adjust the spacing between the poles so the square has bends that are tight enough for your horse, and leave the corners open so the horse can pass in and out between the poles.

You could, for example, lunge so the horse goes outside the poles, inside the poles, or alternates one outside and one inside. Varying it this way makes the horse a little more attentive and helps it find its balance through the bends. Come out and mix this with work on a straight line, placing two cones on the other short side where you can work on halt and rein-back. Raise your hand a little in the halt and rein-back if she tends to go behind the vertical, and see whether you can get better self-carriage there.

Ridden:

You can then do exactly the same. Keep yourself in balance, and feel that you are sitting centrally over her on the bending line, where it is easy for us as riders to sit crookedly and collapse to one side. Think about enlarging and reducing the circle gently as you change its size. If you need to slow down, do it by taking your hand a little upwards at the front to help the horse lift through the ribcage.

Good luck!