Flack was born in Enfield, London, and attended Great Hockham Primary School and Wayland Community High School in Watton, Norfolk.
She got her break in 2002 on television playing Bubbles on the sketch show Bo’ Selecta! In 2005 after moving to Channel 4,Flack presented links between videos on E4 Music and co-presented The Games: Live at Trackside on E4 with Justin Lee Collins.She also had a regular segment on the video games show When Games Attack.
A year later, she co-presented the Saturday morning show TMi with Sam and Mark, which aired on BBC Two and the CBBC Channel.
In March 2007, Flack hosted the CBBC coverage of Comic Relief does Fame Academy,commenting on the semi-finals of the Eurovision Song Contest 2008 with Paddy O’Connell. She also hosted Big Brother’s Big Mouth during Week 5 of the 2008 series.
In 2009, Flack replaced Kirsty Gallacher as co-host of Gladiators with Ian Wright for the second series on Sky1 and filled in on the BBC’s Sunday show Something for the Weekend, while Amanda Hamilton was on maternity leave. She also began hosting the ITV2 reality show I’m a Celebrity… Get Me Out of Here NOW! this however made her quit TMi due to filming clashes with I’m a Celebrity . She also won BBC Three’s Dancing on Wheels with disabled partner James O’Shea and the pair represented Great Britain in the 2009 Wheelchair Dancing European Championships in Tel Aviv, finishing 16th in their category.
In 2010,Flack co-presented game show The Whole 19 Yards with Vernon Kay on ITV. On 16 February 2010, she presented backstage at the 2010 BRIT Awards on ITV2.
In May 2011, Simon Cowell announced that Flack and Olly Murs would co-present the eighth series of The Xtra Factor, replacing Konnie Huq. Flack and Murs both returned for the ninth series. Flack returned for the tenth series in 2013, while Murs was replaced by Matt Richardson. She was however, replaced by Sarah Jane Crawford for series .
Flack along with Murs replaced Dermot O’Leary as the hosts for the 12th series of The X Factor but On 22 February 2016, confirmed that they would not be returning for the 13th series and were permanently replaced by O’Leary.
She began presenting ITV2’s Love Island in June 2015 and its spin-off show Love Island: Aftersun when the third series aired from June 2017.
In August 2014, Flack was announced as a contestant on the twelfth series of Strictly Come Dancing. Her professional partner was Pasha Kovalev. The couple earned the first perfect 40 of the series for their salsa in the semi-finals, followed by an additional 3 in the finals giving them a perfect total of 120 points. The pair were crowned champions of the series on 20 December 2014.
In 2011,Flack made headlines after news broke that she was in a relationship with One Direction member Harry Styles who was 17 at the time.She was 31.
On December 14th 2019,Flack was accused of assaulting her boyfriend,former tennis professional,Lewis Burton, after police found him covered in blood when he called them to her Islington home.Flack denied the charges and Burton insisted that he was not a victim instead describing himself as a witness.On 17 December 2019, she announced that she would be standing down as host for the sixth series of Love Island following the allegations.She was due to go to trial on March 2020.
Flack was found dead in her East London flat on 15 February 2020. A family confirmed that she took her own life.
Two days before her death, she posted photos of herself with her dogs, with no message except a simple love heart. Before that, her last message was on Christmas Eve – the day after her court hearing.
“This kind of scrutiny and speculation is a lot to take on for one person to take on their own…” she wrote.
“I’m a human being at the end of the day and I’m not going to be silenced when I have a story to tell and a life to keep going with.
“I’m taking some time out to get feeling better and learn some lessons from situations I’ve got myself into to.
“I have nothing but love to give and best wishes for everyone.”