Phillips moved to Brighton in 2008. She was elected to represent the Goldsmid ward on Brighton and Hove City Council in a 2009 by-election, and re-elected in 2011. In subsequent council elections she contested the Regency ward, winning a seat in both 2015 and 2019. She became Brighton's youngest mayor in 2019 after being selected for the role by her fellow councillors. She finished her term as mayor in May 2020. Outside of her council roles, she has worked as the policy lead at the HIV and sexual health charity, Terrence Higgins Trust, and as a French and German language secondary school teacher in Croydon, London, and later Hampshire. In 2022, Phillips announced that she and her husband were stepping down as councillors ahead of the May 2023 elections.
