The Dragon's Demigod | WTS AU

We all know the story of Percy Jackson, savior of Olympus, son of Poseidon. But what if he had an equally talented sister, one who was there every step of the way, through all his quests, and someone he could rely on no matter what? What happens when she dies at Gaia's hands, but did she really die? Or did the Fates have something else in store for the demigod daughter of Poseidon?