Fallon is the ninth child in a family of thirteen girls. She was educated in Melbourne and Canberra, leaving school at fifteen. She moved to the Northern Territory in 1980. After having worked variously as a youth worker, store detective, shop assistant, executive secretary, project manager, and computer trainer, Fallon became a full-time writer, inspired and encouraged by her mother from an early age. Her first series, The Demon Child Trilogy, was shortlisted for the Best Fantasy of 2000 in the Australian Aurealis Awards.