Millward ran as the
Green Party candidate in the 2021 by-election for the
Hartfield seat on
Wealden District Council, following the death of councillor Chris Hardy. She won the seat by 122 votes against the
Conservative Party candidate Bruce Rainbow, gaining the seat from the Conservatives. Millward retained her seat in the
2023 Wealden District Council election, with an increased majority of 318. She was appointed joint-
leader of the council in May 2023 alongside the
Liberal Democrat councillor James Partridge, as part of a
coalition agreement between the two parties. In July 2023, Millward was selected as the Green Party's prospective candidate for the constituency of
Sussex Weald, but withdrew in May 2024 over concerns about being both a parliamentary candidate and leader of the council. In June 2025, Millward announced her candidacy for the
Green Party deputy leadership election. Due to
Zack Polanski winning the
leadership election, Millward and
Mothin Ali were elected as joint–deputy leaders, as the Green Party constitution stipulates that if there is a singular leader, there must be two deputy leaders. In October 2025, Millward was selected as the Green Party candidate for
Mayor of
Sussex and Brighton for the
2028 mayoral election. == Personal life ==