Gillies wanted to apply for a specialist course in architectural conservation at the University of York but was told by a tutor that her grades were not good enough.
Twenty-three years after graduating from Liverpool, Gillies did return to York to study conservation of historic buildings, despite by then having her own practice and two small children.
The practice specialised in repair and conservation of historic buildings, architectural design and adaptive reuse, and archaeology.
Gillies' projects include Queenstown's oldest house, Williams Cottage, Arrowtown Masonic Lodge, Balfour Stables in Otago, and the renovations at Speight's Brewery in Dunedin.
"[1] Gillies' work on the Balfour Stables in Otago won the NZIA Local Branch Heritage Award in 2009.