[2][12] Ashley's first acting role was in two episodes of the CBBC fantasy teen drama Wolfblood as Zuhra.

[13] From 2019 to 2021, Ashley played the recurring character Olivia Hanan in the Netflix comedy-drama Sex Education.

[7] Having auditioned in 2020, it was announced in February 2021 that Ashley would star as leading lady Kate Sharma, opposite Jonathan Bailey, in the second series of the Shondaland-produced Netflix romance period drama Bridgerton, based on the second novel in Julia Quinn's Bridgerton series, The Viscount Who Loved Me.

[16] In 2022, Ashley featured in the Forbes 30 Under 30 list in European entertainment,[17] the Time 100 Next,[18] and The Hollywood Reporter's Great British and Irish Film and TV Breakouts.

[19] She appeared on the cover of British Vogue's December 2022 and March 2024 issues, the latter as part of an ensemble of 40 women gathered to honor and celebrate Edward Enninful's tenure as editor.

[10] She played Indira known as Alana, a sister of Ariel in the 2023 live-action film adaptation of Disney's The Little Mermaid.