Unremarkable by Viola Grace

A scheming vampire, a unicorn with a job to do, and a mage who thought her power was gone, leaving her unremarkable.

Ally surrendered her magic as a teen. Her sister was the family heir, and Ally just wanted to leave her home and start off in a new city. She takes on odd jobs and ends up as a secure courier. Weeks before her twenty-seventh birthday, she takes a delivery that goes wrong and ends up with her being bound to the vampire king of the city. She decides to run, but he thwarts her, and after experiencing brunch with the vampire, she agrees to give him a chance to seduce her.
Being seduced by a vampire takes time. There has to be formality, organization, and an opener. Ally had never heard of openers, but they were used when there were physical issues between the more aggressive of the races and usually the hapless human. The openers were unicorn stallions with a talent for easing things between normally incompatible species. Ally agrees to it, but there is one problem. She knows the unicorn.
Bastien was the brother of one of her best friends, and he had been in training when she had seen him last. She had never imagined that she would see him again and that he would see all of her.
Ally had sought to live her life quietly, to be unremarkable, but now, she was in the spotlight, and her family was calling her to defend her life, her freedom, and her new mates. She was taking her family down.