My Super Sister by Gwyneth Rees
Emma knows that having superpowers isn't always easy, especially when you have to keep them secret. But it's even harder when your mischievous little sister can't help using them in the naughtiest of ways. And when Saffie makes the new nosy neighbours' garden shed come to life and hop over the hedge it's up to Emma to cover its tracks before it's too late!
Being a big sister has never been so heroic!