One of five children born and raised on a council estate in Bushey, near Watford, Hertfordshire, Holliman intended to train as a horse riding instructor. However, after she developed hay fever at aged 18 and with nothing else to do, her then boyfriend Andrew Ridgeley suggested she come and dance while he and his friend George Michael's band did a local gig.
Holliman was never a band member of what became Wham!, but, like her friend Dee C. Lee, was paid on a per performance basis as backing singers, and continued to live with her parents. After Lee left to marry Paul Weller, she was replaced by "Pepsi" Demacque, and this duo performed on all the Wham! songs and concerts. As George Michael desired to create music targeted to a more sophisticated audience than Wham!'s primarily teenage fan base, the announcement of Wham!'s break-up was made in the spring of 1986, with a grand finale concert at Wembley Stadium on 28 June 1986, called The Final.
During their Wham! career, Holliman and Demacque decided to form their own act, named Pepsi & Shirlie. Created immediately after the Wembley concert as an upbeat and more pop genre sound, they had two UK Top Ten hits: "Heartache", which was produced by Phil Fearon and Tambi Fernando, reaching #2 in the UK Singles Chart behind the #1 hit of George Michael and Aretha Franklin's I knew you were waiting, and "Goodbye Stranger", produced by Tambi Fernando and Pete Hammond, reached #9.
The hits dried up from 1988, and, as Holliman married Spandau Ballet bassist and singer Martin Kemp, the duo naturally came to an end after the birth of her daughter. Holliman had met Kemp through mutual friends in the theatre in 1980, and the pair married in St. Lucia in 1988. They have two children: daughter Harley Moon Kemp (born August 1989), and son Roman Kemp (born January 1993). Holliman and daughter Harley had brief roles together in the Spice Girls video Mama.
After Holliman took time out to care for her husband through his illness with brain tumours, she was declared bankrupt in September 1996, and the family moved from Hampstead Heath to Muswell Hill to allow Kemp to recover. This enabled Pepsi & Shirlie to return briefly in 2000 to record their backing vocals on the UK number one Geri Halliwell hit Bag It Up.
No longer active in pop music performance, Holliman now manages a business associated with music and entertainment production, Aegean.