Here's her story - via my interactions and reference from Wikipedia and from Davies, in her published memoirs The Times We Had.
Marion Cecilia Elizabeth Brooklyn Douras was born on January 3, 1897, in Brooklyn, the youngest of five children.
The Douras family lived near Prospect Park in Brooklyn. Marion and her sisters changed their surname to Davies, which one of them spotted on a real-estate agent's sign in the neighborhood.
Even at a time when New York was the melting pot for new immigrants, having a British surname greatly helped one's prospects—the name Davies has Welsh origins.
Educated in a New York convent, Davies left school to pursue a career. She worked as a chorus girl in Broadway revues and modeled for illustrators Harrison Fisher and Howard Chandler Christy. In 1916, Davies was signed on as a featured player in the Ziegfeld Follies.
After making her screen debut in 1916, modelling gowns by Lady Duff-Gordon in a fashion newsreel, she appeared in her first feature film in the 1917 Runaway Romany.Davies wrote the film, which was directed by her brother-in-law, prominent Broadway producer George W. Lederer.
Playing mainly light comic roles, she quickly became a film personality appearing with major male stars, making a small fortune, which enabled her to provide financial assistance for her family and friends.
According to her own audio diaries, she met newspaper tycoon William Randolph Hearst long before she had started working in films. In 1918, Hearst formed Cosmopolitan Pictures and signed Davies to a $5-per-week contract, using his newspapers and Hearst Newsreels to promote her.
Hearst's over-the-top promotion of her career, in fact, had a negative result.
Hearst, who was still married, became romantically involved with Davies and moved her with her mother and sisters into an elegant Manhattan townhouse.
Cecilia of the Pink Roses in 1918 was her first film backed by Hearst. She was on her way to being the most infamously advertised actress in the world.
The 1922–23 period may have been her most successful, with both When Knighthood Was in Flower and Little Old New York ranking among the top 3 box-office hits of those years. Indeed, she was named the #1 female box-office star by theater owners and crowned as "Queen of the Screen."
Hearst loved seeing her in expensive costume pictures, but she also appeared in contemporary comedies.
King Vidor saw Davies as a comedic actress instead of the dramatic actress that Hearst wanted her to be. He noticed she was the life of parties and incorporated that into his films.
After seeing photographs of St Donat's Castle in Country Life magazine, the Welsh Vale of Glamorgan property was bought and revitalized by Hearst in 1925 as a gift to Davies. Hearst and Davies spent much of their time entertaining, holding lavish parties with guests at their Beverly Hills estate.
The coming of sound made Davies nervous because she had never completely overcome a childhood stutter. Her career continued, however, and she made several comedies and musicals during the late 1920s and 1930s.
She was involved with many aspects of her films and was considered an astute businesswoman. Her career, however, was hampered by Hearst's insistence that she play distinguished, dramatic parts as opposed to the comic roles that were her forte.
Davies officially retired. In 1943, Davies was offered the role of Mrs. Brown in Claudia, but Hearst dissuaded her from taking a supporting role and tarnishing her starring career. In her 45 feature films, over a 20-year period, Davies had never been anything but the star and always got first billing. The only exceptions were films in which she appeared as herself and uncredited cameo appearances.
When Cosmopolitan folded, Davies left the film business and retreated to San Simeon. Davies would later state in her autobiography that after many years of work, she had had enough and decided to devote herself to being Hearst's "companion and confidante."
Decades after Davies' retirement and death, however, the consensus among some critics is more appreciative of her efforts, particularly in the field of comedy.
And that's where I come in...