Glamour - Rae Wilder, #1

Rae Wilder has problems. Supernatural creatures swarm the earth, and humanity is on the brink of extinction. Stalked by a handsome fairy who claims she is like him, demonkind, Rae thinks maybe it was a mistake breaking the rules by going over the Wall into demon territory. Plunged into a world of dark magics, fierce creatures, and ritual sacrifice, she is charged with a guarding a magical amulet. The changes to her mind and body are startling, but rather than accept her purpose she struggles against who she is destined to be.
Throw in a big lust for a vampire who can't keep his hands off her, and life starts to get complicated.  Rae is forced to make the ultimate choice: to live and die human, or embrace her birth-right and wield magics that could turn her into something wicked, a force of nature nothing can control.