Lavinia lived in Africa and India with her husband for many years, but moved in with her unmarried sisters at The Old Manor House in Jocelyn St. Mary when she became a widow. Her husband died about four or five years before the events of the novel, and they never had any children. She also has a small house near Hampton Court, outside of London.
Miss Marple judges Lavinia to be a good many years younger than herself, perhaps fifty years old. She is described as being "plump, good-natured, and friendly though a little shy", and "plain but pleasant-looking".
When Miss Marple first arrives in Jocelyn St Mary, Lavinia comes to the Golden Boar to ask her to stay at The Old Manor House with her and her sisters. She tells Miss Marple that Mr Rafiel had suggested this in a letter, written before he died.
When Miss Marple is sitting in the drawing room of The Old Manor House, with Clotilde and Anthea, Lavinia leaves them to go to the kitchen, and Miss Marple obseres that she seems to be "the active domestic one of the three".
Lavinia later tells Miss Marple that she worries about her sisters. She says that Clotilde has always been strong and tough, but she worries about Anthea, who is vague.
When Miss Marple mentions the name "Verity" in front of the three sisters, Lavinia drops the book she is holding, and looks surprised. She tells Miss Marple that it is a name with which they have associations. She later tells Miss Marple in private about how Verity Hunt had lived at The Old Manor House, had made friends with Michael Rafiel, and had later disappeared. She tells Miss Marple that Verity's body was found in a ditch, and Clotilde had to go and identify the body, and had never quite gotten over the shock.
Lavinia says that she wished she had known Verity better, as she and her husband were living abroad during the time when Verity was living at The Old Manor House. They had come home on leave once, but had mostly been in London.
Miss Marple later explains that because Lavinia was not in Jocelyn St Mary at the time of Verity's death, she did not know the truth of who killed her.