An American playwright, short story writer, and novelist, she is particularly known for her 1928 dramatization of Edith Wharton's famous novel, The Age of Innocence. Barnes is also remembered for her 1930 novel, Years of Grace, which won the Pulitzer Prize.
She graduated from Bryn Mawr College in 1907 and subsequently worked as the college's alumnae director.
Her 1935 novel, Edna, His Wife, was adapted into a stage play by Cornelia Otis Skinner.
She married Cecil Barnes in 1910. One of the couple's three sons, Edward Larrabee Barnes, became a prominent architect.
Her dramatization of Edith Wharton's novel, The Age of Innocence, was the basis for a 1934 film of the same title.