Atkinson did her high school studies from Castlebrook High School. Atkinson gained popularity with the role of Lisa Hunter in the juvenile novel of Channel Hollyoaks. Marcus Patric and she also appeared in the sequel named Hollyoaks-Let Loose on channel E4. On April 2009, she finished recording an episode of The Bill. Her role as Ria Crossley, a trafficker's girlfriend. She appeared in the independent British film Boogie Woogie, which was premiered at the Edinburgh International Film Festival on June 2009. She finished recording a horror movie called 13hrs (sic).
In theatre, Atkinson appeared in Peter Pan at the Manchester Opera House in December 2008. She had the lead role over John Thomson who played Captain Hook. Gemma is currently performing in a Tim Firth production called Calendar Girls at the Noel Coward Theater, between July 28 and October 17 where she starred as Elaine. She made her debut in video games when appearing in Command & Conquer Red Alert 3 (2008) in the role of Lieutenant Eva McKenna, she participated in the sequel Command & Conquer Red Alert 3: Uprising (2009). She was also present at the Electronic Arts event "Be the One" in Trafalgar Square on October 29, 2008, which was part of the London Games Festival. She also starred in the Goldie Lookin Chain music video "R'n'B" and appeared on the album cover.
In 2011, she joined as a recurring role in the Casualty series where she played the paramedic Tamzin Bayle, until 2012. On May 24, 2014, she returned to the series again and his last appearance was on Oct 11 of the same year, after her character decided to leave after her fiance Jeff Collier, died during an accident. In 2015, she joined the main cast of the series Emmerdale Farm where she played Carly Hope, the daughter of Bob Hope, until June 2, 2017, after his character decided to leave Emmerdale to start a new life with his ex-boyfriend Matt. She worked for the On Yer Bike London campaign as a prelude to the Tour De France. She has also modelled for lingerie brands, including the image of La Senza and Ultimo Lingerie. In September 2007 Atkinson organized a 5km charity race to raise awareness about breast cancer.