Marshall was an unsuccessful
Labour candidate for the St Andrew's Ward in 1924. She was elected as a Councillor for Sutton Ward in 1925. She was appointed Alderman in 1950 and Lord Mayor 1950–51. A lightweight robe and a featherless
tricorn hat were made for her on her election as Lord Mayor. She only had a telephone installed in her house when she became Lord Mayor. She retired as an Alderman and from the Council in 1961. Marshall was chairman of
Moorhaven Hospital Management Committee, vice-chairman of
Plymouth, South Devon, and East Cornwall Hospital Management Committee, and a member of the
South West Regional Hospital Board. She was awarded the OBE in
1955.
Lady Astor was awarded the Freedom of the City in 1959, but the Labour Councillors boycotted the event because the
Conservative Councillors had refused to award Marshall the Freedom at the same time. ==Personal life==