She is the moon:

Prologue

"These creatures must be destroyed!"

"Let them live – they are not that bad!"

"They are a danger to our children!"

"You will not touch them!"

"SILENCE!" The mighty Zeus screams. Silence reigns through Olympus. He looks around at his council and sighs. "What is the meaning of this nonsense!?"

Artemis slowly stands up. "My lord, Aphrodite and Hades have created a type of monsters that have been feasting on mortals and one of her things just killed one of my hunters!"

"Who was the girl?" Zeus questioned.

"Angela Simmons." Artemis says. "Daughter of Demeter."

"HOW DARE YOU!" Demeter screams "ZEUS I DEMAND YOU DESTROY THESE CREATURES!"

"Demeter, you and I both know that I can't destroy these creatures if some of them are innocent." Zeus begins "So I have an idea, we will have a few members of our council go down onto Earth and do an investigation on the creatures. Any volunteers?"

No hands are raised.

"Very well then," Zeus begins "I shall pick. Okay… Ares I want you to go south by Texas, Demeter you can go to the Amazon, and Artemis and Apollo... I want you two to head to the West Coast."

"Are you serious?!" Artemis shrieks "My lord, my hunters. They need me! You can't leave me with HIM!"

"Aw c'mon little sis! It'll be fun! We will be in sunny California!" Apollo says happily.

"Actually" Zeus begins "I was thinking more of Washington."

Apollo's smiles falters. "Are you sure?"

Zeus just gives him a warning glare. "You two will be going as father and daughter and will be located twenty five miles south of Port Angeles, Washington. Now, Aphrodite, do you have a name for these creatures?"

"Vampire"