She looks lovely! What I would say is that the horse is a little too big for her to get into a good riding position so the position is not her fault at all. The distance between her body and the horses neck is too far for her. Her arms are straight and they chouldn't be. Again, not her fault. She is also sitting a little too far back in the saddle which is making her lean forwards. I think if you put her on a pony which suits her size, her riding position for english riding would be excellent and then we could do a proper critique. However, I think good for you letting her get used to different sizes of horses. She will grow into them eventually. She could ride my Clydesdale (18.2) anytime and he would love her!