Magnusson descended from a family of Swedish cabinetmakers, and was a woodworking apprentice at furniture manufacturer, Kärnans in Helsingborg after she graduated from high school. Starting with this internship, where she was the only woman, Magnusson realized the hardships of being a female designer and she said since then she felt she “had to be a step ahead or else”. In 1928, she earned a place at Konstfack in Stockholm, to study Furniture Design. She later studied architecture at the Royal Academy of Technology in Stockholm. She became successful in being “ahead or else” and was the first woman to win the Furniture Design Award from the Swedish Society of Industrial Design in 1933. That same year, she married the British jazz musician Billy Grossman in 1933.
In 1940, amidst the World War II, she left Sweden and emigrated with her husband to Los Angeles where they opened the Magnussen-Grossman Studio on the prestigious Rodeo Drive. The studio focused on furniture and lighting design and sold to several well-known furniture companies such as Sherman Bertram, Martin Brattrud, Cal-Mode and Barker Brothers' Modern Shop.
She was influenced by European Modernists and the Bauhaus, including Walter Gropius and Ludwig Mies van der Rohe. Characterized by its unique utilization of materials and slender proportions, her designs captivated a Hollywood clientele, among which were stars such as Greta Garbo and Ingrid Bergman. In 1943, her split-level house in Beverly Hills was the first project that allowed Grossman to stretch the glass ceiling and play the parts of both interior designer and architect. The house was a major breakthrough for her and Between 1949 and 1959 she designed fourteen houses in Los Angeles.
In 1950, MoMA awarded Grossman with the Good Design award for her Cobra Lamp. With her work in the U.S, characterized among “Los Angeles Modern”, she became an important figure in the experimental architecture world in the 1960s. She also shared her knowledge: Grossman was a professor and lecturer at UCLA in Furniture Design between 1957 and 1963. Today especially her lighting designs are highly sought after by affluent collectors and sold by the most prestigious auction houses and dealers. Grossman’s designs are a part of art and design history, exhibited in museums worldwide, including MoMA in New York and The National Museum in Stockholm.