In HMS Surprise, Maturin meets Diana in India, where she is living under the protection (i.e. as the mistress) of a wealthy civilian, a married man named Canning.
There she explains the difficulties she faces, being financially dependent on Canning and at the same time rejected and covertly insulted by most of her equals in that small, bigoted community.
Before the ship in which the recovered Maturin travels can catch hers and the marriage can take place, she goes to the United States with Johnson, an American she met in Calcutta.
She and her lady's companion, Mrs. Wogan, are questioned as spies by an incompetent admiral, sending Villiers away as innocent, while her friend negotiates a sentence of transportation to Botany Bay, on the ship that Jack Aubrey captains.
In The Yellow Admiral, the two travel in Spain with Brigid, Padeen and Mrs Oakes, so Stephen can share the places special to him with his wife and his daughter.
Diana is a resourceful woman, pawning her Blue Peter diamond for 50,000 pounds, so they are not pinched, and she can ride and breed horses, at which she is highly skilled.
When her cousin Sophia relates her marital issues, Diana and Mrs. Oakes give her a new perspective on marriage, how she might get more enjoyment from sex, which conversation is learned by her retelling it to her husband.
Diana enjoys driving a carriage and team of horses, exhibiting high skill in carrying her husband and Jack Aubrey across a narrow bridge, while bringing them to the coast to return to their ship.
Diana makes her final appearance in The Hundred Days, in which she and her aunt, Sophie's mother, are killed when the carriage runs off a bridge at a dangerous corner.
At a seminar hosted by the Smithsonian Institution in 2000; Washington Post contributor Ken Ringle described Diana as a "bitch-goddess" and "one of the very greatest female characters in all fiction.
"[2] In a series retrospective interview, author Rachel McMillan praises O'Brian's depiction of Diana, noting the character's strong independence.