In the audition, they sung ’Popular’ from the musical ”Wicked”, however they were criticised for their song choice by Simon. Amanda defended them during their critique. They still got 3 yeses from the judges.
In the semi-finals, they sung 'Girls Just Wanna Have Fun' by Cyndi Lauper.
Before BGT Demi had a part in a film named Hell's Pavement.
Later in 2009 she appeared in an advertisement for the second series of The Inbetweeners. After her appearance on Britain's Got Talent Megan went on to appear on Ex on the Beach, The Only Way Is Essex (wherein she auditioned to be part of girl group LOLA and later performed alongside them at T4 Stars of 2010), Celebrity Big Brother, There's Something About Megan, Celebs on the Farm, Celebs Go Dating, and The X Factor: Celebrity, ultimately winning the latter.
In 2017 McKenna released two singles, 'High Heeled Shoes' and 'Far Cry From Love' which peaked at #43 and #53 in the Official Singles Chart respectively. In May 2017, McKenna launched her own restaurant, "MCK Grill", in Woodford Green. Later in 2017, she released a range of hair extension pieces with Easilocks.
In December 2017, McKenna embarked on her first headlining tour to promote the release of "High Heeled Shoes", which consisted of four dates, visiting The Sugarmill, The Venue, Palace Theatre and Scala. In July 2018, she supported Michael Bublé at the British Summer Time show at Hyde Park. On July 26th 2018, McKenna released her debut autobiographical book, Mouthy, published by John Blake, with the book going on to top the Sunday Times bestseller list. In August 2018, she released her debut clothing range, Studio Mouthy, which accompanied her makeup range, Mouthy Cosmetics. McKenna released her debut album Story of Me on December 7th 2018. The album peaked at #4 on the UK Country Chart.
From May 2019 to September 2019, McKenna embarked on the Story of Me Tour across the United Kingdom. In February 2020, McKenna began recording her second studio album, and later that month, it was announced that she was set to support Lionel Richie on the British leg of his tour.