Gwendolyn's father is a Highborn from Myst. He was one of the Dark Queen's most loyal warriors. She sent him to Earth to study and learn more about humans. That's when he met a human woman and raped her. Her mother was pregnant with Gwen when the Myst's guardians hunted her father and killed him.
Already hungry while still in the womb, Gwen fed on her mother's bones and chewed her way outside of her mother. Punishing herself by starving herself, her wings wilted away over time.
She must condume a child's first tooth to restore her powers to full strength, but she craves human bones instead.