Marsh was born in 1887 in Newcastle. Her father, Arthur Hardwick Marsh, was a noted watercolour artist. She was educated locally at St Margaret's School and then at Roseneath in Wrexham before completing her education in Bordeaux. Charlotte Marsh joined the Women's Social and Political Union in 1907, at the age of 20. She did not, however, become active in the movement until 1908 when she finished her training as a sanitary inspector.
During her first WSPU deputation to Parliament Square in June 1908 Charlotte was arrested for obstruction, and imprisoned in Holloway for one month. The following year she became WSPU Organiser in Yorkshire. Whilst in prison in 1909 for heckling Asquith, Charlotte became one of the first hunger-striking suffragettes to be forcibly fed.
In 1910 Charlotte became the WSPU Organiser in Oxford and subsequently Portsmouth and Nottingham. As well as working as a full time paid regional Organiser, Charlotte also continued to undertake militant acts. For smashing nine windows in the Strand in March 1912 she was sentenced to 6 months imprisonment. Organisers like Charlie were vital to keeping the Suffrage movement in the public eye and putting pressure on politicians. She was a notable figure in the Suffragette movement, appointed Colour Bearer for the Hyde Park procession of 1910. She marched at the head of this even on 18 June 1910, carrying 'the great silk standard of the WSPU.'
During World War I, when the WPSU announced a "truce" with the British government, Charlotte worked as a motor mechanic, chaffeuse to Lloyd George and as a land girl. By 1916, Marsh was frustrated with the WSPU's refusal to campaign on suffrage issues during the war. She founded the breakaway Independent Women's Social and Political Union to continue the campaign, publishing the newspaper Independent Suffragette.
After the war she worked for the WILPF peace movement and then as a social worker in San Francisco. She returned to London where she returned to her expertise in public health working for London County Council.