Born in Rio de Janeiro and later moving to São Paulo, she began uploading social media content aged ten, before applying for the third series of The Voice Brasil, on which she was a semi-finalist.

[5] When she was young, her parents divorced, and she went with her mother and siblings to live with her aunt and uncle in a household consisting of nine people[6] from her family;[7] she spent her teenage years in São Paulo.

[4] Her brother was a fan of System of a Down,[6] while her grandmother preferred bossa nova, samba, and música popular brasileira[4] and her mother jazz such as Billie Holiday and Chet Baker,[6] and her sister introduced her to bands such as Legião Urbana, Barão Vermelho, and Titãs.

[12] In February 2019, she featured on Møøn by Joe Hertz,[13] Pete Tong's son,[14] which explored women's empowerment through spaceflight, an idea they got from tarot card reading.

She then signed to Black Butter Records, and on 11 July 2019, she released "Million Dollars", a song about empowerment and class discrimination,[15] which was followed by a video fifteen days later.

[27] A music video was released for the song, which was filmed on a used industrial boat on the River Thames beneath Tower Bridge and required multiple takes, causing traffic congestion.

[35] In March 2023, she and Switch Disco performed "React",[36] that band's collaboration with Ella Henderson and Robert Miles,[37] on the Reunion episode of the ninth series of Love Island,[36] and later that year, she released "ATM" featuring Baby Tate, a song about sharing wealth.

[39] Asked by Lock Magazine in May 2021 which "women in pop" had inspired her, Lellis cited Nathy Peluso, Tkay Maidza, Kali Uchis, Doja Cat, and "icons and rulers of pop like Rihanna, Beyoncé, J-Lo, Christina [Aguilera], and Ariana Grande",[24] and in an interview with Notion in July 2021, she further cited Tim Maia, Jorge Ben, Billie Holiday, Stevie Wonder, and Kanye West as inspirations.