Grandmother is a high-ranking human and once worked as Isabella's Mama although she treated her more as a pawn than a human.
SpoilerOn January 27, 2046, it was revealed that all of Isabella's mistakes and responsibilities, as in letting the children escape, were placed on Grandma Sarah. Although Isabella wasn't able to manage her products, Sarah wasn't able to manage Isabella. As a result, Sarah was shipped out to be served at the upcoming Tifari in order to make up for the escapees. Isabella took the role of Grandmother after that.