Sorry for misunderstanding your post but as far as leaving her lower half alone we will just have to agree to disagree. She needs to fix the stepping out issue and she needs not have a bent front leg at contact. If you think both things are fixable with just focusing on upper half OK but I think they can be fixed by focusing on them specifically.
Let me try it a different way with you. What do you see her doing wrong with her lower body other then where her front foot lands?