The grand-niece of Ralph Waldo Emerson, she spent much of her early life in New York. A graduate of Barnard College, she attended the Art Students League for three years, studying with Kenneth Hayes Miller, George Bridgman and Leo Lentelli. In the summers of 1923 and 1924 she attended the American Academy at Fontainebleau, France, where she learned fresco painting from Paul-Albert Baudoin, a former student of Pierre Puvis de Chavannes.

In the summer of 1925, while a guest of Mabel Dodge Luhan's at her compound in Taos, New Mexico, she met her future husband and noted sculptor, Arnold Rönnebeck, and socialized with authors Aldous Huxley and D.H. Lawrence. After their marriage in New York in 1926, attended by Mable Dodge and Tony Luhan, the Rönnebecks relocated to Denver where he served as director of the city's art museum for five years until resigning in 1931.

Proficient in oil, tempera and watercolor, Ronnebeck frequently painted children, using her son and daughter as models. She also depicted historical events, Colorado's abandoned mines and ghost towns, and scenes from city life. A considerable portion of her work comprises mural painting during the 1930s and 1940s. It derived from her training with Baudoin in France and from her interest in the work of Mexican muralists Diego Rivera and José Clemente Orozco.

While raising her two children and running the family household, she entered sixteen competitions for mural commissions under the various federally-sponsored art programs during the Great Depression. She won two of them: Harvest (1940, Grand Junction) now in the city's Wayne Aspinall Federal Building, and The Fertile Land Remembers (1938, Worland, Wyoming) now in the Dick Cheney Federal Building in Casper.

Ronnebeck also received commissions for frescoes and murals in Denver and elsewhere in Colorado, many of which have not survived: Kent School for Girls, Morey Junior High School, Denver City and County Building, Church of the Holy Redeemer, Bamboo Lounge at the Cosmopolitan Hotel, Robert W. Speer Hospital for Children, USO Men's Service Center, Denver Area Methodist Church, Albany Hotel and Weld County Hospital in Greeley, Colorado.

From 1945 to 1951 she worked as Assistant Professor of Drawing and Painting in the College of Fine and Applied Arts at the University of Denver. In 1948, with some of her artist colleagues at the university, she became a founding member of the 15 Colorado Artists, the group that split from the Denver Artists Guild.

Following the marriages of her two children, Ronnebeck moved to Bermuda where the Emerson family had spent many vacations. She taught at the Bermuda High School for Girls and executed her last mural for St. Brendan's Hospital in 1966; it was destroyed in a later renovation. In 1973 she returned to Denver where she spent her remaining years.