The Second Summoning — Tanya Huff

CLAIRE HANSEN WAS A KEEPER...
gifted--or cursed--with the job of being one of Earth's Guardians, "Summoned" to areas where anomalies existed, where rifts had opened--or had been opened. Such places were the world's danger spots where, if they weren't sealed in time, all the minions of Hell might break through.

After she'd closed the portal into Hell at the Elysian Fields Guest House, Claire and her talking cat, Dustin, found they'd acquired a new companion--Dean. Though Dean was a Bystander and shouldn't have been allowed to even remember Keepers existed, somehow in the course of their mutual ordeal at the Elysian Fields, he'd become an indispensable part of Claire's life. She knew she should change his memories and force him to leave her. Any other course was bound to lead to disaster. But as it turned out, it was already too later for without Dean around Claire could easily become a danger to herself and the very fabric of space and time.

Yet with Dean around--and a little of her sister Diana's meddling thrown in--the world was headed straight for Chaos. And Claire was about to face a challenge beyond her wildest imagining--a catastrophe created by the power of love--when an angel and a devil each manifested in the mortal world as fully endowed teenagers, who didn't have a clue how to handle their all-too-human bodies, raging hormones, and opposing needs to do good anti evil....