Williams was born 10 May 1960,[1] at Scorrier House, Cornwall. She started as an amateur National Hunt jockey, she rode in the Grand National in 1988 and fell at Bechers Brook, and another fall 2 weeks later at Worcester Racecourse, she was forced to retire after sustaining a broken neck.[1] She worked for racehorse trainers Martin Pipe and John Edwards, before herself taking up a licence to train in 1995.[1]
In 2009, she won the Grand National with 100-1 outsider Mon Mome.[2] This victory made her only the second female trainer to win the race, after Jenny Pitman.[2] After the race, even Williams was shocked by the outcome, saying, "How can you ever expect that? It's unbelievable."[2] She also trained Teeton Mill, winner of the Hennessy Gold Cup and King George VI Chase in 1998.[3]