In the novel 4.50 from Paddington, Geraldine Webb is mentioned by Miss Marple. Miss Webb was always vert quiet, and was dominated by her elderly mother. After the death of her mother, Geraldine went on a holiday. When she returned she had, much to everyone's surprise, married a nice lawyer.
When Miss Marple met Emma Crackenthorpe, she was reminded of Geraldine Webb.