[8] She has also served on the board of anti-violence organisation Our Watch, on the WA Ombudsman's Advisory Committee on Child Death Reviews and Family Violence Homicides, and on the Indigenous working group for the Every Woman Treaty campaign.

Siewert chose to resign from the Senate prior to the end of her term, creating a casual vacancy to be filled by Cox in September 2021.

[15] She took her maiden speech as an opportunity to shine a light on First Nations issues, including cultural heritage, rates of homelessness, deaths in custody, Treaty and family violence.

[16] In November 2021, Cox secured the support of the Senate to establish a parliamentary inquiry which will examine the policing processes used in First Nations murder and missing persons investigations.

In response, a spokesman for Cox stated that "the number of staff that had left the senator’s office was not unusually high and said part of the reason for the turnover was her shift into the First Nations portfolio during the Voice to parliament referendum campaign".

[20] In 2020, Cox stated that her priorities if elected to the Senate would be to work for treaties with Indigenous Australians and to establish a national family violence strategy.

[10] Following the 2021 Australian Parliament House sexual misconduct allegations, she stated that the women's rights movement in Australia suffered from a lack of diversity.

[24] Cox moved amendments on behalf of the Australian Greens to prohibit Export Finance Australia from investing in fossil fuel projects.