Lynn supported the workers during the 1913 lock-out and worked with Constance Markievicz and others in the soup kitchens in Liberty Hall, becoming close to Markievicz and James Connolly. In 1913, at Markievicz's request, she treated Helena Molony. Molony, who was active in a number of political movements, stayed with Lynn in her Rathmines home following an illness. As a result of the influence of Molony and Markievicz, Lynn became an active participant in the suffragist, labour and nationalist movements. "We used to have long talks and she converted me to the National Movement," Lynn wrote. She joined the Irish Citizen Army and was chief medical officer during the 1916 Easter Rising. She described herself as "a Red Cross doctor and a belligerent" when she was arrested.