A Pixie Wish

Yudi is an orphan girl who helps a pixie and in return is granted a wish. This wish takes her to where the pixies live. She is accidently bitten by a younger pixie and almost dies from it. No one has ever been allergic to pixie bites. The queen of the pixies comes to visit Yudi and finds out a secret from the girl's past that will shock everyone. What is the secret?