In the authorised Miss Marple continuation short story The Murdering Sort, Diana Westover is the daughter of Michael Westover and cousin of Sarah and Harry. Diana had been to a public school in England where she met and befriended Nicola West. At school, Diana had been extremely popular, not only because of her background as a glamourous New York heiress but also because of her sense of style and intelligence.
Despite her wealth, Diana is not very much concerned about business or money. Her passion is with protecting the environment. She tells Miss Marple, who is holidaying at Cape Cod that large parts of the beautiful seashore there is about to be ruined by development. She tells Miss Marple that she misses "the old days" although she is actually too young to remember them. Just ten years earlier she could remember frogs singing from the pond across from grandfather's house and now she doesn't hear anything.