Orman was born in Sydney, but grew up in Canberra and Melbourne and spent two years living in the United States. She earned a degree in microbiology at Sydney University before becoming a professional author. She is a self-described "liberal feminist". She is married to American writer Jonathan Blum, whom she met through Doctor Who fandom.
Orman penned many spin-off novels from Doctor Who for Virgin Publishing, BBC Books and Telos Publishing. Several of her later Doctor Who works were in collaboration with her husband. She has also collaborated with Paul Cornell: Orman and Cornell co-plotted Human Nature, written by Cornell, and Return of the Living Dad, written by Orman. More recent Doctor Who and related work has been for Big Finish.
Orman has also had a number of short science fiction stories published.
In 2004, Orman and Blum's Doctor Who novella Fallen Gods, published by Telos the previous year, won the Aurealis Award for best Australian science-fiction book.