The Blood Bride by Rae D. Magdon

Valis Nyxera Aefbain, queen of the snow elves, must find a consort of magic blood as soon as possible. A dangerous secret slumbers beneath her palace and only a powerful ritual can keep her kingdom safe. Brynn Woodwarden, a wood elf with misfiring magical abilities, hates the snow elves. They killed her brother, Darrow, while poaching unicorns. But dangerous creatures prowl her forest home−twisted, Rotted things that infect anyone they bite. The wood elves can't fend them off alone. Only Brynn's unique blood is suitable for Valis' ritual. Only Valis has the soldiers and alchemists Brynn needs to stop the Rotted creatures. An arranged marriage is the perfect solution−but such a union might be more than either of them bargained for.