I taught third grade for a few years before moving to Sweden. I had a student that behaved the same way. He was a very bright student but for a short time he was riding his "high horse". His mother was very concerned because she knew that as intelligent as he was he had much to learn.
This is what we did. I placed him into the fifth grade reading class. It was too advanced for him and he came back to me asking if he could go back to his previous class. It worked for him. Every child is different but it may work - even if it is some kind of extra curricular activity. You don't need to give her an activity that she would fail at but perhaps something that she'll really need to work at. It may just be enough for her to realize that not everything is a breeze and even bright and intelligent people sometimes need to work a little harder to achieve their goals.
Best of luck to her!
