Marshall is the owner of the St. John's-based legal practice Stapleton Chambers. She is among the top lawyers in the country.[2]
Marshall won the St. Mary's South constituency in the 2014 general elections defeating Hilson Baptiste, a member of the United Progressive Party. Six days after the 2014 elections, she was appointed Minister of Social Transformation and Human Resource Development by Prime MinisterGaston Browne.
She won the same seat in the 2018 elections and was appointed Minister of Social Transformation, Human Resource, Youth, and Gender Affairs Department one day after the 2018 elections.
She became a senator on 23 January 2023, after losing her seat in the 2023 Antiguan general election.[3] Marshall resigned from the Senate on 13 November 2024.[4]