Shadow Blood: Book 4 of The Witch Fairy Series

After years of trying, Xandra's aunt has finally figured out astral projection. Unfortunately, she astral projects her and Zac's souls out of their realm and into the Shadow realm. Or, as some like to call it - Hell. Xandra has no choice but to go in after them; otherwise, their souls will be trapped there forever. But first, she has to convince the Angel of Death to let her in, and they don't exactly hit it off when they first meet.