The Wingless Fairy Series, Book 8: Rebecca and the Dragon by Margaret Pearce

Dragons aren't supposed to exist in the mortal world. But when livestock begins vanishing and strange wings blot out the stars, Rebecca knows something ancient and dangerous has arrived.

A dragon egg is about to hatch, and every dragon in existence is gathering to fight for the right to become consort to the new Princess. Among them is Perjury, a monstrous black dragon who breaks every law of his kind. Something darker controls him from the shadows. Something that shouldn't have escaped its prison.

Rebecca is just a mortal girl now, no longer the fairy princess she once was. But the Fairy Queen has asked for her help, and dragon law doesn't apply to humans. With her loyal owl companion, two devoted house goblins, and a terrified silver dragon named Albus hiding in her creek, Rebecca must find a way to stop Perjury before the full moon rises.

Can one small girl give a cowardly dragon the courage to face his destiny? The answer begins with a bucket of bright red oats and a promise that she says twice a day, every day, no matter what he wails back.