Stolen Dreams by H.G. Lynch

Having left her life at Acorn Hills behind, Ember tries to pick up the pieces of her heart at home in Scotland. Reuniting with old friends, working a normal job, hiding her fangs...
But while fake smiles fill her days, nightmares plague her nights, re-opening the wounds she's tried so hard to heal.
Left behind in Acorn Hills, Reid spirals into a deep depression, becoming more and more self-destructive. Until Hiro takes pity on him and comes up with a solution to the hollowness left by Ember's absence: get her back.
With the way Ember left, Reid knows it won't be easy to win back his Firefly, but he will do it. He has to.
Otherwise, an eternity without her isn't something he could live with.