Angel From Heaven (Harry Potter Maurauders FanFic)

Ariel Michaels is a magical human-witch being. She has every power element, water, air, fire, and earth. She goes to Hogwarts school of Witchcraft and Wizardry. She can also shape shift into anything, has the ability to control things with her mind, and has super speed.
She welcomes the first years, and uses her powers against the forces of evil, and she's only fifteen.
But one day, she has to join the dark side.mTo protect Hogwarts, the only home she's ever known. And everyone inside.
But she finds herself falling for the one and only Sirius Black. But he'll never like her, especially since she's led everyone to believe she's betrayed everyone that has ever trusted her.
Then her secret gets out. And her life is in danger. And so are the lives of the people she loves.