Lorne was born in West Pittston, Pennsylvania, a small mining town halfway between Wilkes-Barre and Scranton. She was the daughter of william Lorne MacDougall MD, and his wife, Jane Louise (née Oliver), known as "Jennie". She was born in 1883 (although by the 1920s she had shaved five years off of her age). While her year of birth is listed as 1885 in some sources, including the date inscribed on her urn (which appears to be erroneous), it was usually listed as 1888 when she was alive. The 1900 United States Census (enumerated in June 1900) gives her age as 16 and, along with the Social Security Death Index (SSDI), lists her year of birth as 1883. Her parents were Scottish and English immigrants. She had a younger brother, Lorne Taylor MacDougall (October 20, 1893 – September 5, 1943). She studied at the American Academy of Dramatic Arts in New York City.
Lorne debuted on Broadway in 1905; she also acted in London theaters, enjoying a flourishing stage career on both sides of the Atlantic Ocean. In London she had her own theater, the Whitehall, where she had top billing in plays written by Walter C. Hackett, her husband. None of her productions at the Whitehall had runs shorter than 125 nights.
In 1911, she married Playwright Walter C. Hackett. They were married until his death in 1944. The couple had no children.
After appearing in a couple of Vitaphone shorts, including Success (1931) starring Jack Haley, she made her feature film debut in her late 60s in Strangers on a Train (1951), directed by Alfred Hitchcock. From 1952-55, she was seen as perpetually confused junior high school English Teacher Mrs. Gurney on Mister Peepers.
From 1957-58, she co-starred with Joan Caulfield in the NBC sitcom Sally in the role of an elderly widow who happens to be the co-owner of a department store. Although afraid of live television, declaring "I'm a coward when it comes to a live [television] show", she was persuaded to appear a few times to promote the film The Girl Rush with Rosalind Russell in the mid-1950s. Between 1958 and 1964, she made regular appearances on The Garry Moore Show (1958–1962).
She appeared in 27 episodes of Bewitched, and was not replaced after she died of a heart attack in her Manhattan apartment prior to the start of production of the show's fifth season, on May 9, 1968, aged 84. She is buried at Ferncliff Cemetery in Greenburgh, New York.
