In the novel The Mirror Crack'd from Side to Side, Mrs Hartwell lives in “the Development” in St. Mary Mead, and is the next door neighbour of Cherry and Jim Baker. Cherry and Jim do not get along with her.
According to Cherry, when she and Jim listen to music in their home, the Hartwells start rapping on the wall as early as twenty minutes to eleven sometimes, and are always asking them to turn it down low. Cherry describes Mrs Hartwell as a "sour-faced old cat, always gossiping and complaining". Jim also mentions the Hartwells' cat, which comes into their garden and digs up the beds.