O'Sullivan is known for her unique, dramatic musical style and covers of artists such as Radiohead, Tom Waits, and David Bowie.
[7] O'Sullivan took a year off from her studies[citation needed] and moved to Berlin, Germany, where she worked at an architect's office.
During her time in Berlin, she regularly attended local cabaret clubs[5] and began listening to the narrative music of Hanns Eisler, Kurt Weill and Friedrich Hollaender.
Upon returning to Ireland, she met Agnes Bernelle, a mentor who encouraged her to sing, saying "to do this right, you have to be a better actress than a singer, it's all about the story.
[5] After being spotted by Ewen Bremner performing La Clique in The Famous Spiegeltent, O'Sullivan appeared as the vaudeville star Jane in the film Mrs Henderson Presents, directed by Stephen Frears, opposite Dame Judi Dench and Bob Hoskins.