She was a member of the Congressional Union for Woman Suffrage (CUWS), where she served as the North Carolina Field Secretary.

[1] In New Mexico, Thompson worked with Adelina Otero-Warren to recruit members for a new chapter of the CUWS.

[3] In 1916, she traveled to Missouri campaigning for Republican Charles Evans Hughes' failed presidential candidacy.

In 1917, Thompson traveled with Alice Paul to work on setting up a new branch of the National Woman's Party (NWP).

The following year, 1919, Ella was arrested outside of the Metropolitan Opera House, demonstrating against Woodrow Wilson.