Complex sentence: Helen Torr (1886-1967) was an American painter who worked with other artists, namely her friend Georgia O'Keeffe and husband Arthur Dove, to develop a characteristically American style of Modernism in the 1920s.
Split into simpler sentences: Helen Torr (1886-1967) was an early American Modernist painter. Torr worked alongside other artists, namely her friend Georgia O'Keeffe and husband Arthur Dove, to develop a characteristically American style of Modernism in the 1920s.