Murao Mima

Key says that Dr. Mima brought her into this world, that he is her "Creator". But she also refers to him as her "Grandfather". He is a pioneer in robotics, but he couldn't develope a robot that would move from his own will, untill he met Tomiko (Key's grandmother) and her Geist in Mamio Valley... Their daughter Toyoko provides him with a liquid manifestation of her and her mother's supernatural powers, which he uses as a "gasoline" for his dolls/robots. Toyoko didn't want the same fate for her daughter Tokiko, so Dr. Mima fulfilled his daughter's will of supressing all supernatural powers in Tokiko by hiding all the extracted gel inside her. Unfurtunately this act also supressed her human conciousness.

Therefore Key believed she's another robot of Dr. Mimas'.