Defiant Princess by Jayne Faith

The safety of royal life shatters in an instant . . .
Karna Dunjour dreams of learning weapons and combat. Instead, the princess is stuck at a prestigious foreign university with other dragon shifter royals. It doesn’t help matters that Karna sucks at her studies, especially compared to her charming and talented twin brother and their perfect older sister.
But when an enemy tribe attacks the school, the safety of royal life shatters in an instant. The strike aims to wipe out the Dunjours, forcing Karna and her siblings to flee.
Fearing the worst for her family back home, Karna must find a way to survive. With the help of handsome and mysterious Dmitri, Karna finds a man who can show her how to exact vengeance. But she’ll have to abandon her identity and enter a shadowy world. Can Karna become the assassin who will save her family, the throne, and her people?