Heiss was educated at St Clare's College, Waverley, then at the University of New South Wales, where she earned her Bachelor of Arts degree in 1989. After a cadetship at the Australian International Development Assistance Bureau (later AusAID) in Canberra, she returned to UNSW to complete an honours degree in History in 1991.[2] She gained her PhD in Communication and Media at the University of Western Sydney in 2000, becoming the first Aboriginal student at the university to achieve this, which she considers her proudest achievement.[3] While working on her doctorate, Heiss ran writing workshops in regional New South Wales, and also travelled to Canada and New Zealand to do research there, giving several guest lectures while abroad.[2]
After attaining her doctorate, Heiss taught an Introduction to Indigenous Australia course at the University of Western Sydney, but became disillusioned with academia and resigned her position after a year or two, although retaining her unpaid role as an adjunct associate professor at the Badanami Centre for Indigenous Education at the university,[2] a position she continued until at least 2011.[4]
Heiss was a consultant researcher and writer for the Barani Aboriginal history website, first published by the City of Sydney in 2001.[6]
Heiss was appointed to the State Library of Queensland board in 2017.[18] As of 2021[update] she is not on the board, but a member of the Indigenous Advisory Group, an independent advisory group to the Library Board.[19]