@Itsn Seems she is using magic to hide it so she can better hide in the human village. Considering she seems to effectively be a retainer for Dou, she probably did that so she can gain trust easier... enslaved human vs. strong ass demon.
Might be a mistranslation (there's often errors with orders of magnitude in numbers), or have something to the house being so close to the demon kingdom.
Pfft. As if Dou needs something as weaksauce as mind control powder to make people give her huggies and headpats. Or do basically anything for that matter.