Diana Barry is a central character in the anime Anne Shirley, known primarily as the cherished best friend of the protagonist, Anne Shirley. Diana is established as a main character and is the first true friend Anne makes after arriving at Green Gables. She is depicted as a girl of about twelve years old at the time of her introduction, belonging to one of the wealthiest and most respected families in the rural community of Avonlea.

Physically, Diana is portrayed as a very pretty girl with striking features. She has long, lustrous black hair that reaches her waist, often styled with hair loops and ribbons, and sparkling black or dark blue eyes. Her complexion is fair with rosy cheeks, and she is frequently seen wearing fine dresses with fashionable puffed sleeves, a detail that Anne greatly admires. While her appearance is a source of envy for the freckled, red-haired Anne, Diana herself is said to have a constitution that tends toward being chubby, and she sometimes envies Anne's slender figure.

The personality of Diana Barry is marked by a gentle, kind, and good-natured disposition. Unlike the imaginative, impulsive, and outspoken Anne, Diana is calmer, more sensible, and has a more conventional temperament. She comes from a morally upright and well-regarded family, and her upbringing has made her polite and well-behaved. Despite their contrasting personalities, the two girls form an immediate and deep bond. Diana has a remarkable ability to understand Anne, who is often seen by others as odd or dramatic, and she accepts her friend's eccentricities with patience and loyalty. While generally agreeable, Diana is not without a sense of propriety; she has, on occasion, chided Anne for being too harsh or unforgiving, such as when Anne refused to accept Gilbert Blythe's apologies.

Diana's primary motivation throughout the story is to maintain her deep friendship with Anne and to be a supportive presence in her life. She serves as a confidante, a grounding force, and a loyal ally. Her role in the story is almost entirely defined by her relationship with Anne Shirley, acting as her bosom friend and the sister of her heart. She is a key figure in several of the most memorable incidents in Anne's early life in Avonlea. In one famous event, Diana visits Anne for tea, and Anne accidentally serves her currant wine instead of raspberry cordial. Unaware of what she is drinking, Diana becomes intoxicated, which leads her mother, Mrs. Barry, to believe Anne acted maliciously. This results in Mrs. Barry forbidding the two girls from seeing each other, a separation that causes both of them great distress. The crisis is resolved when Anne heroically saves the life of Diana's younger sister, Minnie May, who has fallen dangerously ill with croup while their parents are away. Diana’s desperate plea for help brings Anne to her home, and Anne's quick thinking and knowledge of the illness stabilize the child until a doctor arrives. This act of bravery not only saves Minnie May but also restores Anne's standing with the Barry family, and the two friends are happily reunited.

Diana’s key relationships are central to her character. Her most significant relationship is, without doubt, with Anne Shirley, whom she considers her lifelong kindred spirit. She is the older sister of Minnie May Barry, whom she loves and for whom she is responsible. She is the daughter of Mr. and Mrs. Barry, who are strict but loving parents. Her relationship with her mother is tested during the wine incident, but it is repaired following Anne's rescue of Minnie May. She is also the niece of the formidable Aunt Josephine Barry, with whom she and Anne have an unexpected and lasting connection after being discovered sleeping in her guest bed without permission. At school, she is friends with other girls like Jane Andrews, but her bond with Anne remains the most profound.

As the story progresses into later arcs, Diana's development continues. While Anne goes on to pursue higher education at Queens Academy and later Redmond College, Diana is unable to attend due to her father's opposition. Instead, she remains in Avonlea, eventually marrying a local farmer named Fred Wright, a fellow member of the Improvement Society, and becomes Diana Wright. She has several children, including a daughter she names Anne Cordelia, a tribute to her dearest friend. Although their lives take different paths, with Anne engaging in academic and intellectual pursuits, Diana's loyalty never wavers. She continues to be a steadfast friend, offering a connection to Anne's simpler, more innocent childhood days. In one instance, thinking she is being helpful, Diana secretly submits one of Anne’s short stories to a contest run by a baking powder company. When the story wins, Anne is initially mortified to see her work used as an advertisement, but she later appreciates Diana's good intentions.

Notable abilities of Diana Barry are less about special talents and more about her personal qualities. Her primary ability is her quiet aptitude for providing unwavering loyalty, emotional support, and sensible judgment. She is depicted as a stabilizing influence in the more tempestuous life of Anne Shirley. She is also shown to be capable of creating candle signals to communicate with Anne from her house, indicating a resourceful and playful side to her nature. Ultimately, Diana Barry is portrayed as the embodiment of a faithful and true friend, whose gentle kindness forms the perfect complement to Anne Shirley's passionate and imaginative spirit.