Started riding at the age of four. Mary competed as an eventer until being introduced to dressage by her first husband, Gert Donvig.

Competed at four Olympics: Atlanta (Mosaic), Sydney (Limbo), Athens (Limbo) and London (Sancette) and at two WEGs, Rome 1998 and Jerez 2002. In 2014, won the right to represent the Pacific League at the World Cup Final in Lyon, on Sancette.