[2] Mitchell started athletics in 2000, inspired by the success of compatriot Cathy Freeman at the Sydney Olympics, but stopped at the age of 12 to concentrate on netball.

[3] Mitchell's father is an African American former professional basketball player who moved from the United States to Australia, and her mother is Australian.

[4][5] Mitchell competed in the 4 × 400 metres relay event at the 2015 World Championships in Beijing without advancing to the final.

In 2019, Mitchell switched focus to the 800 metres, rapidly improving to her current personal best of 2:00.06.

[7] As part of her switch in event, Elizabeth Mathews became her coach and Mitchell began running 60–70 km a week rather than the 15 km per week she had done for sprinting previously.