Ashworth was born in Manchester in 1969. She studied at Hertford College, Oxford, where she was a scholar. She later became a Junior Research Fellow of Jesus College, Oxford. Once in a House on Fire, published in 1998, won the Somerset Maugham Award from the Society of Authors in 1999. It tells the story of her traumatic upbringing and the abuse that she suffered at the hands of her two stepfathers.