The duke of the north...wait what?

Fantasy settings

You were just finishing a fantasy romance novel when you suddenly fell asleep. You woke up and realized your surroundings changed! It turns out you got Isekai-ed as the female lead of the novel you were just reading...but it ended in a tragedy! You decided you wanted to change your fate by asking help from the duke of the north yet it seems like he...or she has a secret that the novel never disclosed.

THE NOVEL'S PLOT (BASICALLY):

The female lead is the youngest daughter of the king which led her to be overlooked most of the time. The king openly shows favoritism towards his eldest son, Carl, who is also the heir to the throne.

When a neighboring prince named Roderick took a liking to the female lead, he threatened their kingdom war if they don't give the female lead to him.

She tried to run away yet was caught by her brother, Carl. In the end, she was sent to the neighboring prince to get married yet was poisoned to death by the prince's former lover.

{Also I may or may not have gone overboard on the initial message)