Somers moved to Dalkey, County Dublin in 1908 with her mother who was again taking a position as the town postmistress. From here Somers was an active member of The Gaelic League and Sinn Féin, as well as a supporter of Cumann na mBan and the Irish Volunteers. She eventually became the secretary of the local Cumann na mBan unit. Somers' campaign against Irish recruitment into the British Army in 1915 led to her mother losing her job as postmistress of Dalkey. This made her the first civil servant to lose her job due to her association with Irish republicanism. Her persistent lobbying of Matthew Nathan through correspondence led to her mother being reinstated at the end of World War I. Her brother, D.C. Somers, was sentenced to five years' penal servitude due to his participation in Easter 1916, and lost his job in the civil service. These led to the family suffering financially. Both her brothers, D.C. and Michael, served in the IRA during the Irish War of Independence. Somers was a public speaker and raised funds for Sinn Féin from 1917 onwards.