She is the first female World Short Course champion in the 1500-metre freestyle, winning the inaugural event for women at the 2022 edition.

[6] She followed up with a first open water title in the annual Pier to Pub swim in January 2018 at 15 years of age.

[11][12] In January 2019, Pallister won her second-consecutive title in the Pier to Pub open water swim in Lorne, winning the women's event, a 1.2-kilometre race, in a time of 12:20.

[13][7] Two months later, in March at the year's Surf Life Saving Australia Championships in Burleigh Heads, 16-year-old Pallister narrowly won the national title in the 2-kilometre ocean swim ahead of second-place finisher Kareena Lee.

[14] As a 17-year-old at the 2019 FINA World Junior Swimming Championships in Budapest, Hungary in August, Pallister won her first medal, a silver medal, in the 4×200-metre freestyle relay where she split a 1:58.61 for the lead-off leg of the relay, helping achieve a final time of 7:57.87.

[29] Pallister started off 2020 with a third-consecutive open water title in the Pier to Pub swim in January.

[33][34] She also set new Australian and Australian All Comers records in the 1500-metre freestyle with a time of 15:28.33 that made her the fourth fastest female swimmer in the race in history only behind Sarah Köhler of Germany, Mireia Belmonte of Spain, and Lauren Boyle of New Zealand.

[36] As of 30 March 2022, Pallister ranked second globally for the 2022 year in the long course 1500-metre freestyle, only behind Katie Ledecky of the United States.

[39] On the third day, she swam a personal best time of 1:57.23 in the prelims heats of the 200-metre freestyle, qualifying for the final ranking fifth.

[40] On the first day of pool swimming competition at the 2022 World Aquatics Championships, Pallister qualified for the final of the 400-metre freestyle ranking third with a time of 4:03.71 in the preliminaries heats.

[44] The following day, she ranked fourth in the preliminary stage of competition in the 1500-metre freestyle, qualifying for the final with a time of 15:57.61.

[45] She won the bronze medal in the final the following day, finishing in a personal best time of 15:48.96, which was less than five seconds behind silver medalist Katie Grimes of the United States.

[46][47][48] It marked the first time an Australian woman won a medal in the 1500-metre freestyle at a FINA World Aquatics Championships.

[53] On day four of swimming competition at the 2022 Commonwealth Games, Pallister ranked first in the preliminaries of the 800-metre freestyle with a time of 8:32.67.

[80] In April, at the 2023 Australian Swimming Championships in Gold Coast, Queensland, she won the silver medal in the 800-metre freestyle with a time of 8:24.72.