I would do this drill that Amanda Scarborough does. It is similar to the K drill. Make sure the drive foot is starting on her toes and her stride foot is around 45. Makes sure she finishes shoe laces to catcher and knee to knee. This will help her stay tall and her arm will stay more tight to body.
https://www.youtube.com/watch?v=Di4xi_jW8Yw
https://www.youtube.com/watch?v=Di4xi_jW8Yw