Daughter of Castiel (Supernatural/PJO Crossover

Grace Singer is pretty happy where she is. She likes traveling around the country, saving people, hunting things. She like's doing it with the Winchesters, who've been like her brothers as far back as she can remember. One day, while on a hunting trip, the trio come across a group of teens, and that's when things get weirder, well weirder for a hunter, that is.
(Cover art isn't mine, I don't own Supernatural or PJO/HoO, just a couple of my OCs)