Rachel,Pianos are awfully big when you're six years old. Octaves are an enormous reach. But I'll stick to my guns: Find out HER favorite songs, and get her to work on those with little scale runs incorporated "for flair."
You might also ask her parents if someone is making faces at her when she tries to practice (or, if you're in the UK, practise) at home. A sibling can be a royal inhibitor.
Sarah