The Siren's Call

As a foster child, Megan is all too used to making connections with people and seeing them leaving. So when a strange girl approaches her and begins to be friendly, she is wary. Then Megan is offered a part in the strange girl's "family." Never having a family before, Megan accepts, becoming a part of the siren sisterhood.
Megan immediately begins to show promise and is later told by the goddess of sirens herself that she will be one of the most powerful sirens that has ever lived.
But Megan is given the task of defeating Lady Juliette, the sister siren who has appointed herself leader. Megan must become powerful enough and learn to perfect her new gift before she is able to defeat Lady Juliette. She must somehow reveal all the lies that Lady Juliette has said to be the rules of being a part of the sisterhood.