Responses
Judging from the fact that she must be someone who was in that family even before he was born, maybe even from the time of the first Duke, she is probably not human and she probably knows something, thats why she's acting this way. She must have build her trust with this family over many years and they're aware she would not harm them for no reason. It looks like she's some kind of guardian of this family and they respect her even though they dont like her actions.
Why hasn’t the dad beat her ass? Plus he doesn’t have to keep the promise with the white hair boy… like he already gave her the blood