Born in Berkshire, Mackay was brought up in Scotland and educated in Switzerland. She trained at Edinburgh College of Art under William Gillies, graduating in 1965, and undertook postgraduate studies at the Central School of Art, London in 1973. Alongside her career as a professional artist, painting portraits, landscapes and still-life and exhibiting widely, Mackay has worked as a teacher of art, design and ceramics. Her paintings are characterised by bold brushwork and vibrant colours. Mackay lives in Edinburgh.