All Sulla knows about her past is she was buried alive with enough magic in her blood to damage her body.
As a baby, the Fey used her as a lab experiment before abandoning her. Now a sixth grader, she's obsessed with heroic tales of overcoming impossible odds. The Fey want her back, and abduct her from her adoptive family. She turns to her stories for guidance. Achieving the impossible requires black and white thinking along with great physical cost.
The Fey do not follow her logic. They are kind and frightening towards her, or useful yet murderous. Amongst themselves they argue whether to keep her on tap, use her as a bargaining chip, or kill her to preserve their secrets. If Sulla wants to return home, she must sacrifice her well-being. Failure will leave her at the mercies of the capricious Fey.