Mystery of the Fallen — C. Lee Tocci

It was a year of firsts for 16 year old Misty Hill. Her first summer love. Her first kiss. Sort of. Her first cellphone. Her first time meeting fallen angels. And her first time being hunted to the four corners of the earth by an army of demon assassins. But that's not her biggest problem. Her biggest problem is the battle in her own heart as she finds herself torn between Cade and Danel, two fallen angels who have pledged themselves to protect her from the hordes of the demon lord, Sam Jaza. Assuming they don't kill each other first.