Enslave Me Sweetly
Eden Black walks among humans, protecting them from the murderous evil of other-worlders who abduct and enslave. And though she appears to be human herself, Eden is an alien, a Raka, distinguished by her golden hair and skin, and gifted with the ominous ability to kill without remorse—and with total accuracy. That is, until the fateful night she has one shot to eliminate her target, a human slaver—and misses.

"Failure" is not in Eden's vocabulary. Neither is "partner"—but that's what she is forcibly assigned after recovering from her disastrous mission. A sexy, steely-nerved human agent, Lucius Adaire enjoys nothing more than sparking the fury—and rousing the desire—of the fiery female assassin too proud to admit defeat. Locked in an assignment they cannot afford to lose, Lucius and Eden find themselves bound in two high-stakes, heart-pounding games: the sensual web of kill or be killed, and the erotic dance of seduction.
Assassins, Human-alien encounters, Fiction, Romance - General, Romance - Adult
Gena Showalter
Gena Showalter is a bestselling author of over thirty books in paranormal and contemporary romances, as well as young adult novels. Her novels have appeared in Cosmopolitan Magazine, and Seventeen Magazine, and have been translated all over the world. Source: Goodreads.com 
"Gena Showalter (born 1975 in Oklahoma) is an American author in the genres of contemporary romance, paranormal romance, and young adult. Showalter sold her first book at the age of 27, and has published over 25 books." - Wikipedia