Kelly studied music performance (oboe) at the University of Auckland, later focussing on composition.
After finishing first equal in the University of Auckland composition prize concert, winning a TVNZ Young Achievers Award, and being awarded a professional development grant from Creative New Zealand, Kelly studied film composition at the University of Southern California.
In 2007, she received a NZ Screen Award for her soundtrack for the television series Maddigan's Quest.
[3] As well as her composition and orchestration work, Kelly was the featured vocalist for the song Beautiful Skin with the New Zealand group Strawpeople.
[8] Musicians, film, and television directors that Kelly has worked with, in addition to those mentioned above, include Neil Finn,[9] The New Zealand Symphony Orchestra,[7] The Auckland Philharmonia,[7] The New Zealand String Quartet, Anika Moa, Shapeshifter, Harry Sinclair, Peter Jackson, Jonathan King, and Robert Sarkies.