Oh I see! So is the grandmother's life similar to Yukino's life? Like you get what I mean, Yukino and Nobora, Miyuki and the Dorm Mother. Nobora and the Dorm Mother are like serious and introverted and a closed up person and both are from the Botan division (I don`t know how to describe them) But on the other hand Miyuki and Yukino are kind, happy and similar to each other and are from the other division. And even tough they are from different divisions they are closed friends, well I believe Miyuki and the Dorm Mother are very close friends.
Maybe the Dorm Mother is Nobora`s grandmother too, but I don`t think that will happen haha