[3] She was a member of the teams that won bronze medals at the 2018 Commonwealth Games and the 2016 Pacific Rim Championships.

[2] Mizzen made her international debut at the 2013 Australian Youth Olympic Festival and helped Australia win the team bronze behind China and Great Britain.

[10] She then made her senior international debut at a friendly meet against China and placed seventh on the uneven bars.

[12] The same team competed at the Pacific Rim Championships to prepare for the Test Event, and they won the bronze medal behind the United States and Canada.

[18] Mizzen won the bronze medal on the uneven bars at the Melbourne World Cup behind Chinese gymnasts Liu Tingting and Luo Huan.

[25] She was selected to represent Australia at the 2018 Commonwealth Games alongside Georgia-Rose Brown, Alexandra Eade, Georgia Godwin, and Emily Whitehead.

Mizzen and Godwin were both sick at the training camp immediately prior to the Games, but they recovered and were still able to compete.