She spoke in defense of Jane Addams and against the National Women Suffrage Association adopting an amendment that would prohibit any officer or member from participating in a major political party in 1912. She was elected to the board of directors of College Suffragist, part of the National Women Suffrage Association, at that time. She led the Equal Suffrage League to try to get suffrage to go to Missouri voters in 1914, but when the state senate tabled the discussion, she and Mrs. Walter McNab Miller, the state Equal Suffrage League president, started a petition campaign. The measure failed at a rate of nearly 3 to 1 statewide. At the 1916 National Democratic Convention, when thousands of women took to the streets to draw attention to suffrage, O'Neil stood at the end of a "golden lane" of women representing states with full suffrage, where she was dressed as a "spirit of liberty."