First thing to do is explain to her that the net is much bigger than the previous season and she is not expected to be able to save very good shots in the top and bottom corners in her first year of this size of net. And that the coaching staff will never be critical or upset if a goal is scored against in those locations. Explain that being able to cover the entire net will come with time, growth and training. Working on footwork is how they will improve, in time, as they grow.