Heline: Helen and Aline After City of Heavenly Fire

Due to her faerie blood, Helen Blackthorn is sent off to excile in a rarely visited island in the middle of nowhere for those there to decide where her loyalties lay. Her fiancé, Aline Penhallow (soon to be Blackthorn) goes with her, furious at the injustice being done to her love. But things don't go quite as planned...
(Helen and Aline [from the general series] as well as the basis for this story are from Cassandra Clare's "City of Heavenly Fire" of The Mortal Instruments series)