The Story of the Female Lead's Father

As the title suggests, this uses a common palace-intrigue trope: the heroine's parents are killed by a treacherous minister, so she enters the palace for revenge and climbs the ranks, from palace maid to empress... She battles in the palace, rises to power, and eventually avenges her parents... But this story is about the heroine's father. He and his male best friend are deeply in love, and after he gets himself killed, he leaves his daughter to avenge him... That's the story.