Mackenzie's notable screen credits include Sarah Beckenham in the BBC's BAFTA nominated series Outlaws, Jackie Haggar in ITV's Hot Money (since remade in Hollywood as Mad Money), and Sally opposite Kris Marshall in the rom-com Catwalk Dogs.
On the big screen she has been seen as Paola Fonseca in Possession (2002), as Jane Graham opposite Timothy Hutton in The Kovak Box (2006), as TV chef Kathy King in Steel Trap (2007), and Teri in Franklyn (2008).
Most recently, Georgia completed a well-received turn as LEA chief Jennifer Headley in BBC One's hit television drama, Waterloo Road.
She also appeared in three episodes of Casualty "Secrets and Lies", "Mistakes Happen" (2013) and "Bad Timing" (2014) as Carol Walcott.
In 2019, Mackenzie narrated the documentary series Cop Car Workshop for the TV channel Dave.