Shadowgirl

Imogen Elinor Smith, ten years old, of London, England, is a demigod.
Yes: one of her parents is one of the Greek gods.
Of course, such a life isn't all fun and games-although capture-the-flag is a Camp Half-Blood must-and with it comes monsters out to kill.
She must learn to survive the life of a half-blood, making friends and more than a few enemies along the way.
And perhaps she'll find a new family to replace the one she lost.