Barrett became a member of S Club 7 after a series of auditions along with members Paul Cattermole, Jon Lee, Bradley McIntosh, Jo O’Meara, Hannah Spearritt and Rachel Stevens in 1999. She was the oldest member of the group, and they enjoyed five years of enormous success, including four number one singles and one number one album. They also had a series of TV shows, which were: Miami 7, L.A. 7, Hollywood 7 and Viva S Club, and they also starred in a film, Seeing Double. Barrett led some of the tracks on the groups’ albums, such as “I’ll Be There” and “Stronger”. Stronger was set to be a single, but was cancelled when Paul Cattermole left the group. The six remaining members stayed together until 2003, when they split after releasing their greatest hits album.
In 2004, Barrett, along with singers Natasha Beddingfield and Atomic Kitten member Liz McClarnon, recorded a single, a cover of Do Ya Think I’m Sexy? by Rod Stewart. She also released some solo tracks on the internet, such as “I Wanna”, “I’ll Be Your Woman”, “Love Sick”, “All Fired Up”, “Loving the Enemy”, “Making Me Dance”, “Blow My Mind” and “Satisfy Me”.

Barrett is currently recording her debut solo album, which is expected to be released in the near future.