[6][7] When Walshe was 13 years old, she won the silver medal in the 100 metre butterfly with a time of 1:02.17 at the 2015 European Youth Summer Olympic Festival held in Tbilisi, Georgia in July and August 2015.

[8] In July 2019, at the 2019 World Aquatics Championships in Gwangju, South Korea, Walshe placed 35th in the prelims heats of the 100 metre butterfly on the first day of competition with a time of 1:00.85.

[10] On 23 May 2021, at the 2020 European Aquatics Championships held at Danube Arena in Budapest, Hungary, Walshe set a new Irish record in the 4×100 metre medley relay with Danielle Hill, Mona McSharry, and Victoria Catterson at 4:02.93 and placed 11th overall.

[11] Three days earlier she split a 1:001.18 on the butterfly leg of the 4×100 metre mixed medley relay to help place 13th and achieve a new Irish record time of 3:49.08 with Shane Ryan, Darragh Greene, and Danielle Hill.

[12] At the 2020 Summer Olympics in Tokyo, Japan, and delayed to 2021 due to the COVID-19 pandemic, Walshe won her heat, placed 24th overall, and did not advance to the semifinals in the 100 metre butterfly with her time of 59.35 seconds.

[17][18] In the final of the event, Walshe won the silver medal with a time of 4:26.52, lowering her own Irish record she set in the prelims heats and finishing less than one second after Tessa Cieplucha of Canada.

[25] Later in the same prelims session, Walshe qualified for the semifinals of the 100 metre butterfly with an Irish record time of 57.32 seconds that tied her in rank for fourteenth with Margaret MacNeil of Canada.

[26][25] In the semifinals of the 100 metre butterfly, Walshe ranked ninth and attained first alternate status for the final with an Irish record time of 56.68 seconds.

[30][7] On the first day of the 2022 Southeastern Conference Championships, held in February 2022, Walshe split a 22.93 for the butterfly leg of the 4×50 yard medley relay to help achieve a second-place finish.

[53] Later in 2022, she announced she would stay in Ireland and take online classes to continue her education at the University of Tennessee, however she did not compete for the swim team in the autumn due to chronic fatigue following the 2022 Southeastern Conference Championships.