Lillie competes in swimming and currently represents Manly Swimming Club, having started when she was 8 years old. Her recent achievements include winning 5 gold medals at the 2023 Age National Championships and competing in the World Championship Trials. At the Trinbago 2023 Commonwealth Youth Games, Lillie’s best result was a silver medal in the 100m butterfly, only trailing teammate Mikayla Bird. She also won two more bronze medals at the Games. Her aspirations include being selected onto the Dolphins Team and breaking an Australian record.