Williams had a five-year-long unbeaten streak of 151 races in the sprints, beginning with the start of her athletics career in 2005 and lasting until July 2010, when she was runner-up to Stormy Kendrick in the 200 m at the World Junior Championships. Williams is the British youth record holder over the 60 m, 100 m and 200 m. At the age of sixteen, she was the top-ranked British woman over 200 m in 2010.