The Fledgling (Hall Family Chronicles, Book 4)

So when her stepcousins Eleanor and Eddy tell her that she can't fly, Georgie doesn't get discouraged -- she just tries harder She feels a peculiar lightness when she leaps from the top of the staircase, and is even more certain of her seemingly impossible ability when she jumps from the porch and soars to the rooftop before landing safely on the ground. And now that a mysterious Canada goose is visiting Georgie's window on a nightly basis, the Hall family begins to wonder just what Georgie is capable of....