She was born in New Haven, Connecticut, the daughter of Bridget (née Lundigan) and Thomas Quinlan, both Irish immigrants from County Tipperary.
She graduated in 1875 with honors in music, playing Chopin's Polonaise for piano, op.
[2] Ella met James O'Neill at her father's house, and later married him on June 14, 1877 in Manhattan.
In late winter 1885, Ella left her sons with her mother in New York to be with James O'Neill while he was traveling in Denver.
[3] Ella O'Neill later became the model for Mary Tyrone in Eugene O'Neill's final work Long Day's Journey Into Night, which tells the story of the Tyrone family, who closely resemble the members of Eugene's family.