@delta_angelfire
demon sacrifice was "this girl is wild" or something along those lines. I don't remember having read the Beatrice one.
It's the novel isekai where the original character was the queens puppet for keeping tabs on the crown prince and his childhood wife, he's sent off to war to die only to return a hero, he marries the dukes daughter and becomes king (or emperor I can't recall), happy end.
Except now she's (MC) managed to make the crown prince fall for her before he goes off to war, dukes daughter has secured the rights to inherit her fathers title (because women couldn't inherit titles) and they are all fighting together to have him be the king, more or less. Hope that's enough plotpoints to bring it to mind.