The House of Shadows - Michele Skaggs - Bog

Melody Grace always wondered why she could see ghosts and why one killed her great-grandfather seven years ago. On the day of her sixteenth birthday, she discovers the answer. Melody is the Earth Elemental.
Shortly after she realizes what she is, Melody finds the other three Elementals. Together, they embark on a quest in search of a magical land known as the Underground. There, they meet many different creatures and beings thought only to exist in myths.
With help from their guardians, the four of them must train to heighten their powers. They are the only ones who can defeat the evil creature threatening to rise and destroy the world.
However, one Elemental is betraying the others as he is doing tasks for the evil creature. These tasks will lead up to a sacrifice for power so the evil creature may gain strength.
Melody will need to keep her emotions in check while trying to balance her normal and magical life.
Will Melody figure out who to trust?
Will the Elementals be able to stop the sacrifice?