Daughter of Fleming Newbold, president of The Evening Star Company in Washington, DC, and Ethel Seckendorff. Niece of Frank Brett Noyes, president of The Washington Star and honorary president of the Associated Press. Her first husband was Allan A. Ryan, Jr. After having two children, they divorced in 1936.
She married William Rhinelander Stewart that same year, and later had a daughter. Mr. Stewart died 3 Jul 1945. In 1948 she married James S. Bush, uncle of President George H.W. Bush. They divorced in 1952, and she resumed the surname Stewart.
Mrs. Stewart was known as “the most beautiful woman in New York” and was included in the first Best-Dressed List. She was famous for her salon cocktail hours held weekday afternoons.
An iconic photo by Erwin Blumenfeld of Janet in Tiffany jewelry with her face against a mirror has become a classic of photography. It was titled "Woman and Mirror", and was published in Harper's Bazaar in November 1941.