Douglass was born in Penola, South Australia. She attended Annesley College, in Wayville, a suburb of Adelaide. She studied for her BA while working as a Registered Nurse, and later completed her PhD in early modern English History. She became a lecturer in medieval history at La Trobe University, Bendigo. While there she completed her first novel, BattleAxe, which launched her as a popular fantasy author in Australia, and later as an international success.
Until the mid-2000s, Douglass hosted a bulletin board on her website, with the aim of encouraging creative thinking and constructive criticism of others' work. She maintained an online blog about the restoration project of her house and garden entitled Notes from Nonsuch in Tasmania.
In 2008, Douglass was diagnosed with ovarian cancer. She underwent treatment, but in late 2010 the cancer returned. She died on 27 September 2011, aged 54.
She also wrote under her real name Sara Warneke.