A ruffian duchess for a ruffian duke

Briana is a duke's daughter who's been on the battlefield for almost a decade. After ten years of battling, what she comes back home to is a run away younger syster, whom she has to replace in an arranged marriage.
"Father! How can you do this to me? All I ever asked of you was an a few years older, soft-hearted, husband who faints at the sight of blood! Now you want me to marry a younger bloodthirsty man, who also happens be our houses enemy? Have I not dealt with enough enemies?"
"It is his majesty's orders! Did I tell you syster to run away? No! What do you think should we become traitors? Do you expect our entire house to die because you want a cute husband?"
"Yes! I don't care!"
"Guards drag Briana to her room!
Servant! Servants!
Make her look like a decent lady! Her carriage will be here in one hour!"