Smith was originally from West Sussex. Her fatherowned racehorses at the time and she would ride them out at Epsom. She had the distinction of participating in Britain's initial ladies' race. In her youth, she was an international show jumper.
In 2013 Smith trained Auroras Encore to win the Grand National. Ridden by Scottish Jockey Ryan Mania, Auroras Encore won by nine lengths, to Cappa Bleu in second and Teaforthree in third. He was an outsider winning at the odds of 66–1. She became the third female trainer to win the race.