Postlethwaite was raised on a farm in the northern Brisbane suburb of
Caboolture, Queensland. Postlethwaite started her sporting career playing
Oztag, the Australian variation of
tag rugby, and started playing Australian rules football only at the age of 12. In 2014 she won the
most valuable player award for Oztag's 13 Girls Division. Postlethwaite played for
Moreton Bay Lions and won the under-15 division
best and fairest in 2016. Postlethwaite played for
Maroochydore in the
AFL Queensland Women's League (QWAFL). In the 2019 season she won the QWAFL Rising Star Award. During 2019, Postlethwaite also played for the
Brisbane Lions Academy team. Postlethwaite represented Queensland in the
AFL Women's Under 18 Championships. In the
2018 AFL Women's Under 18 Championships, she was selected for the All-Australian team. In the
2019 AFL Women's Under 18 Championships she led the team as captain and was selected once again for the All-Australian team. ==AFLW career==