Stewart was born in Paisley, near Glasgow. She studied German and History of Art at Edinburgh University before attending Chelsea School of Art in London from 1989 to 1993. Stewart's subject matter is both familiar and disconcerting: a nun lying on the ground, a pregnant schoolgirl, twin boys in identical clothes. Her sculptures often resemble plastic toys or donation box effigies. They are usually crafted in plaster or fibreglass then painted. The apparent banality of her figures is offset by a sense of humour and the sinister, as they occupy a twilight zone between the real and the manufactured.