In 2021, her transition bore fruit, winning individual bronze over 400 metres at the 2021 European Athletics Indoor Championships along with relay silver.

Four months later, with nine international medals and four British national titles, Williams announced her retirement from elite track and field athletics.

[11] She took the England Athletics Under-20 Championships in 100 m, in a time of 11.48 s. She then went to Brixen, Italy for the World Youth Championships to take part in the 100 m and 200 m. In the 100 m semi-final, she set a world-leading time for a youth athlete of 11.40 s. In the event final she ran 0.01 s quicker to clinch her first world title, defeating Ashton Purvis and Alison Peter.

In the 200 m final, she ran another youth world leading time of 23.08 s to clinch another gold medal, making her the first girl to achieve a 100/200 m sprint double at the competition.

I knew it was going be a close race and I wasn't quite sure I could come out and perform again, so it's obviously a huge relief and the pressure has lifted a bit."

Williams was the fastest qualifier, but suffered her first defeat in her athletics career by coming second in the final to American Stormy Kendrick.

[citation needed] In the 4 × 100 m relay the Great Britain team was eliminated due to a bad baton exchange between Williams and Rebekah Wilson.

[12] At the European Athletics Junior Championships, Williams won the 100 m setting a new personal best and championship record of 11.18 s, breaking the previous record by 0.03 s.[13] She explained "I've been training better than last year and my times in training have been better than last year so I knew I had 11.1 in me, I've just not had the right conditions until today.

"[14] Within 24 hours, she also won the 200 m in a season's best of 22.94 s – despite a strong headwind of −1.5 m/s to complete a sprint double, an unprecedented achievement for a British woman.

Williams ran a season's best time of 7.29 s and finished second behind Jeanette Kwakye at the Aviva UK Indoor Championships.

In the final, Williams posted a quicker time of 22.92 s (-0.5) to claim a gold medal at the European U23 Championships and her 6th age-group international title.

[20] She finished her indoor season, posting a best time of 7.32 s. On 19 April, Williams competed at the Tom Jones Memorial Invitational at Gainesville, Florida.

[21] That result moved her up to joint 9th on the UK all-time list for 200 m. In July 2014, Williams took part in the 2014 Commonwealth Games, Glasgow as a competitor for England.

She won her first heat in 23.42, progressing to the semi-finals where she finished second in a time of 22.64 behind Blessing Okagbare which allowed her to qualify automatically for the final.

The time moved her to equal second on the UK all-time list, alongside Abi Oyepitan and behind Kathy Cook.

In the final, placed in lane 4, Williams won a silver in a new PB of 22.46s, her second individual senior medal in as many weeks.

[24] In 2021 Williams achieved a rare double at the British Championships, winning a third and fourth national title in the 400 and 200 metres.

Williams has come runner-up to Tom Daley twice (2009 & 2010) for the BBC Young Sports Personality of the Year award.