The Margrave's Daughter & the Enemy Prince, Volume 1

This enemies-to-lovers fantasy romance follows a strong-willed, sword-wielding heroine who takes control of her own destiny. 

Anna, daughter of the Margrave of Halmich, is tired of the expectations placed on women in court. She has no interest in marrying a nobleman because society expects it of her. Instead, she works hard on her swordsmanship and dreams of joining her father on the battlefield someday. Unfortunately, fate deals her a heavy blow: when the hostile forces of the Kingdom of Albion invade and take the Halmich heir prisoner, she is given to the enemy prince in exchange for her brother's life. 

But even in the face of these tragic circumstances, Anna still has plans of her own: 

"I'll infiltrate their ranks as a tribute, and then... I'll defeat the man who killed my father."