Vile Artistry (The Nightling Grimoire Book 1) by June Chevalier

Lilya, a girl with the ability to transform into shadow is banished from her tribe and finds herself a new home under the foster care of a lord. Her recklessness soon causes her to make a mistake which results in her tribe’s safety being compromised. Her lord father is then tasked with locating her tribe under the pressure of the Inquisition. Lilya is thus torn between two choices, redeeming herself by saving her tribe from destruction or saving her stepfather who has taken her and loved her as his own; for if he refuses to take up the task, he would be accused of protecting outlaws and is thus liable to death by hanging.