In the early 1920s she went to Cape Breton to organize mine workers. After returning to Toronto, where her son Jim was born, she organized for the communist-led Industrial Needle Trades Workers Union in the early 1930s. While serving on the IUNTW executive board, she helped lead a general strike of Toronto dressmakers in 1931. That same year, she organized support for coal miners in Estevan, Sask. After a riot in which 3 strikers were killed by the RCMP (see Estevan Coal Miners Strike, 1931), Buller was jailed. While working as a business manager for the communist paper The Western Clarion in 1939, she was again arrested and interned until 1942.
After the war she concentrated on party organizing, managing party publications such as the Tribune and National Affairs. She also participated in the party's National Women's Commission and the Housewives' Association campaign to roll back prices. She retired from full-time party work in the late 1950s but remained politically active until her death.