This is a 1970's or 1960's middle reader. Possibly 1980. A girl named Margot lives in a city with her mother, who has not left their apartment since the father left her. She gets along pretty well by having her groceries delivered and such. Margot gets tired of this and decides to spend the night at a library or something to force her mother to leave the apartment to find her. Not sure if her scheme works or not. A neighbor ends up dealing with the police after Margot is found; I remember her spelling Margot's name for them and telling them "The T is silent" and sounding very proud of this knowledge, like it's a family secret. There is also a boy whom Margot befriends.