Yeah. Maou is just a single person. If a random demon was taken from the demon realm, it's possible that one could be a truly horrible individual. But if Maou has been Maou for pretty much all her life, what manner of a personality would you have her possess? If she's a monarch of an empire, it has to show in her character. Maybe she's preachy, has a holier than thou attitude, and she's always right, and is sure her vision for changing the world is ultimately the very best one, if not the only choice for ending the war. However, if she didn't have such an attitude, do you think she would have sent away all her guards and waited empty-handed for the hero to appear to try to win him over? No, she wouldn't have. It's precisely because she believes so strongly in her plan and views that she betted her life, and maybe her whole domain. In conjunction with that, one can deduce the head maid is somewhat akin or Maou wouldn't have dared to let her into the plan.