She is a registered architect in the United Kingdom and South Australia.
She has 15 years experience in private practice, such as Marks Barfield Architects, and was former Head of the Design Review at the UK's Commission for Architecture and the Built Environment (CABE) for four years.
She was associate government architect in the Office for Design and Architecture SA (ODASA).
In July 2015 Mackay was appointed the South Australian Government Architect.
In this role she leads the Architecture and Built Environment Directorate of the SA Department of Planning Transport and Infrastructure, along with the SA Design Review program.