Howell was a painter of landscape, architecture, flowers and still life. She studied at the Corcoran School in Washington and at the School of Design for Women, Philadelphia, under Harry B. Snell.
She exhibited street scenes at the Corcoran Gallery as early as 1918; paintings and watercolors at the Syracuse Museum of Fine Arts in 1921: nineteen paintings of old Salem doorways at Doll and Richard, (Boston, that same year; and New England Street scenes at Macbeth Gallery, New York, in 1922. In an exhibition the following year at Macbeth's she exhibited flower pieces in which she utilized oriental ceramics from the Metropolitan Museum of Art, and American materials such as wallpapers for backgrounds, from the Essex Institute. She received the Second Hallgarten Prize from the Academy in 1921. She exhibited some of these pieces in 1923 at the Casson Galleries as well as paintings of orchids, sketches for which were done at the estate of Albert Burrage near Boston. In 1926 paintings from a recent Italian trip and New England doorways were exhibited at Vose Galleries.
Howell maintained a studio in the Sherwood Building in New York and summered in Gloucester and Rockport, Massachusetts. In 1934 she married George W. Mixter. After his death in 1947 she married W. Dindlay Downs. In later life she lived at Rockport.
