Speaking at an event related to the movie, Hathaway said she wanted to better understand the emotional and physical demands of portraying a singer. "The person that I spoke to was Charli. I wanted to talk to her about the music; she wrote such amazing music that I was going to perform. But I also just had a lot of questions for her about what her life was like, what the experience of being a singer was," she told People.

In Mother Mary, Hathaway plays a globally recognised singer on the cusp of a major performance, whose life is disrupted by the return of an estranged friend, portrayed by Michaela Coel. The film's soundtrack features original music by FKA Twigs, Charli xcx and Jack Antonoff, with the latter two also contributing as producers. One of the tracks, Burial, has multiple collaborators, including Charli's husband George Daniel.

Hathaway said the process deepened her appreciation for performers, particularly the stamina required to sustain live shows. "I just realised that singers are endurance athletes who can do it all in platform heels. They are the most charming people on the planet and they have this crazy self-belief, like they're so driven to share what's inside of them," she said.

The actor also worked closely with choreographer Dani Vitale, who has toured with major artists, to refine her performance and movement for the role. Despite immersing herself in the musical world, Hathaway said there's a difference between acting and singing as forms of expression. "Less vulnerability is required of me as an actress; I like to share what's inside of me through a filter," she said. Agencies