She won the gold medal in the women's 800 metres event at the 2018 Summer Youth Olympics and at the 2019 Pacific Games.

Small competed in the women's 800 metres event at the 2018 Commonwealth Games held in Gold Coast, Australia.

Later that year, she won the gold medal in the girls' 800 metres event at the 2018 Summer Youth Olympics held in Buenos Aires, Argentina.

[1] In 2019, at the Pacific Games held in Samoa, she won the gold medal in the women's 800 metres event.

[1] Greta carried the Australian flag during the opening ceremony of the 2012 Winter Youth Olympics held in Innsbruck, Austria.