She competed in the ninth series of The X Factor UK in 2012, being the eighth contestant eliminated despite being a strong favourite to win.

She signed with Syco Music shortly after, and released her debut studio album, Chapter One (2014), which reached number one in the UK.

In addition to solo material, Henderson recorded a string of successful collaborations, including the UK top 10 singles: "Glitterball" with Sigma, "This Is Real" with Jax Jones, "Let's Go Home Together" with Tom Grennan, "Crazy What Love Can Do" with David Guetta and Becky Hill, "21 Reasons" with Nathan Dawe, "React" with Switch Disco, "0800 Heaven" with Dawe and Joel Corry, and "Alibi" with Rudimental.

She put on Christmas shows for her family and was encouraged to pursue her love of music and songwriting by her paternal grandfather.

She attended the school at the same time as Dan Ferrari-Lane, who later became a member of the boyband District3 which appeared on The X Factor alongside Henderson in 2012.

[7] Henderson auditioned for series nine of The X Factor in 2012, with the original song called "Missed", which was later included on her debut studio album.

[10] During the show and following her exit, a number of celebrities stated their support and praise for Henderson, including Adele, Lily Allen, Cher, Simon Cowell, Stephen Fry, Nick Grimshaw, Sarah Millican, and Chloë Grace Moretz.

[30][32] It was written by Henderson in collaboration with a number of writers and producers including Claude Kelly, Salaam Remi, Babyface and TMS.

[36] The album also charted in the top 20 in Australia, Austria, Denmark, Ireland, New Zealand, Norway, Switzerland, and the United States.

[42] The collaboration achieved global-wide chart success peaking within the top 20 in the Netherlands, Norway, Sweden, Switzerland and the United Kingdom.

[31][43] In November 2016, Henderson announced that she had finished recording her second studio album, having worked with Danny O'Donoghue from The Script and producer Max Martin.

In June, she featured along with other artists, including fellow X Factor artists Leona Lewis, Louis Tomlinson, Liam Payne, James Arthur, Louisa Johnson and Matt Terry on a cover version of Simon & Garfunkel's song "Bridge over Troubled Water", which was recorded to raise money for those affected by the Grenfell Tower fire in London earlier that month.

Later that year, it was announced that Arthur had recorded a duet with Henderson, reportedly set to be included on her second studio album.

While supporting him on his tour, she performed new songs that were set to be included on the record: "Ugly", "Cry Like a Woman", "Bones", "Solid Gold" and "Let's Go Home Together", her duet with Arthur.

[52][53] Henderson released the single "Dream On Me" with Roger Sanchez on 2 October 2020,[54] and a Christmas song "Blame It on the Mistletoe" with AJ Mitchell on 4 December.

[56] On 20 August 2021, Henderson released the single "Risk It All" with House Gospel Choir and Just Kiddin, followed by a collaboration with the French DJ duo Ofenbach titled "Hurricane" the next month.

[31] In April 2022, Nathan Dawe released a second collaboration with Henderson titled "21 Reasons", which reached number nine in the UK.

Henderson's appearance at the Conservative conference attracted criticism from the LGBT Community, as some felt it was incompatible with performing at Pride Events.

[66] In March, she released her collaboration with DJ Regard titled "No Sleep",[67] shortly followed by the song "Like I Used To" with Sonny Fodera and Paul Woolford in April.

[70] On 27 October 2023, Henderson released her second Christmas song with Irish singer-songwriter Cian Ducrot called "Rest of Our Days".