Her father, John, was working as a tennis coach in Germany at the time of her birth and shortly after relocated his family to Wodonga, Victoria.

The family then settled on the Gold Coast, Queensland when Birrell was three years of age as her father took up a role as the head coach of Pat Cash's Tennis Academy.

[8] Queens Park had previously produced top 20 tennis players such as Bernard Tomic and Samantha Stosur,[9] the latter of whom would train with Birrell when visiting the club.

Following a strong 2012 season, she made her junior Grand Slam debut at the 2013 Australian Open at 14 years of age and was beaten by Sweden's Rebecca Peterson in straight sets.

She gained her first professional ranking point a year later with a straight sets win over Elizabeth James after receiving a wildcard into the main draw of a tournament held in her home state of Queensland.

[12] Birrell was awarded a wildcard into the doubles main draw of the Hobart International with compatriot Olivia Tjandramulia,[14] where they lost in the first round to second seeds Lisa Raymond and Zhang Shuai.

She also made her major main-draw debut, after getting one of seven team wildcards in women's doubles, alongside Priscilla Hon, but lost to the fifth seeds, Raquel Kops-Jones and Abigail Spears.

[16] In March, Birrell qualified for and made the first ITF Circuit final of her career in Mildura, but lost to compatriot Alison Bai, in straight sets.

Birrell was awarded a wildcard into the qualifying rounds of the Brisbane International, but lost to eventual main-draw semifinalist Samantha Crawford.

Birrell and her doubles partner, Priscilla Hon, were given a wildcard into the Australian Open, losing in the first round to Sam Stosur and Zhang Shuai.

The next week, in Gatineau, Birrell and her new doubles partner, Emily Webley-Smith of Great Britain, lost in the final to the same duo - Kuwata and Savinykh - in a third-set tiebreak.

Birrell came back at the end of September with a run to the final in the Penrith International, losing to Olivia Rogowska[20] in two sets.

The following week in Brisbane, Birrell won her first ITF singles title by beating American Asia Muhammad in a tight three-setter.

She played Madison Keys in the first round of the 2019 Fed Cup World Group and lost the match, but Australia won the tie.

[29][30] At the Australian Open, she received a wildcard into the main draw, after the withdrawal of Venus Williams, and defeated 31st seed Kaia Kanepi in a three-set match lasting two hours and 32 minutes.

[35] At the Monterrey Open, she made her second WTA Tour doubles final, partnering local favorite Fernanda Contreras Gómez after receiving a wildcard.

[38] In doubles, she partnered Olivia Gadecki, and together they scored a win over Sabrina Santamaria and Varvara Gracheva in straight sets.

[51] Birrell began her 2025 season at the Brisbane International, where she received a wildcard entry and defeated qualifier Priscilla Hon,[52] second seed Emma Navarro[53][54] and Anastasia Potapova to reach the quarterfinals,[55] at which point her run was ended by Anhelina Kalinina.

[56] Birrell qualified for the Australian Open,[57][58] but lost in the round to lucky loser Eva Lys, after her scheduled opponent, 13th seed Anna Kalinskaya, withdrew just minutes before their match was due to get underway.

[59][60] Partnering John-Patrick Smith, she reached the mixed doubles final, losing to John Peers and Olivia Gadecki.

[61] Entering as a wildcard at the Singapore Open, Birrell defeated fifth seed Polina Kudermetova[62] and Hailey Baptiste[63][64] to make it through to the quarterfinals, where she lost to Ann Li.