Whanau moved to Wellington as an adult to study, and in 2003 won $1.39 million in a Lotto draw, which she used to pay off her parents' mortgage, support her family, and travel.

[11] Her career was mainly in marketing and digital communications, with roles with financial services firms such as Axa, TWUSUPER, and Cigna, as well as the New Zealand charity Plunket.

[12] During the 2017 general election, she was the party's digital director and became acting chief of staff when Deborah Morris-Travers resigned in August 2017.

[18] Whanau announced her intention on 18 November 2021 to run for the Wellington mayoralty in the 2022 election,[7] and formally launched her campaign on 30 June 2022.

Following a month of negotiations and restructuring, she appointed several Labour and Green councillors as chairs of these three council committees (Rebecca Matthews, Teri O'Neill and Tamatha Paul).

[25] Georgina Campbell from The New Zealand Herald wrote that this was in order to build better relationships with independent councillors without a formal party membership.

[28] In mid-March 2024, Whanau supported a plan to permit for more housing construction in Wellington by upzoning vast areas of the city.

[37] In early February 2025, Whanau confirmed that the Wellington City Council would be making a major announcement on the "Golden Mile" area the following week.

On 11 February, the Council confirmed that it would begin plans to pedestrianise the Golden Mile area between Lambton Quay and Courtenay Place in April 2025.

Wellington Chamber of Commerce chief executive Simon Arcus expressed concern that these changes could affect local businesses and emphasised the need for consultation.

On 30 June 2023, a Friday evening, Whanau appeared to employees to be intoxicated upon entry[39] to The Old Quarter restaurant in Dixon Street.

Whanau admitted not paying her bill and being "tipsy" but denied that she had acted confrontationally towards staff members, including asking if they knew who she was.