A Court of Silver Flames by Sarah J. Maas

Nesta Archeron has always been prickly-proud, swift to anger, and slow to forgive. And ever since being forced into the Cauldron and becoming High Fae against her will, she's struggled to find a place for herself within the strange, deadly world she inhabits. The one person who ignites her temper more than any other is Cassian, the battle-scarred warrior. The fire between them is undeniable, and only burns hotter as they are forced into close quarters with each other