The announcement was made live this morning on BBC Radio 1's Breakfast show with Nick Grimshaw. "I think you've just got to go for it because I personally - I always veer away from looking too ultra girly but on this you've got to go for it - get the pink on, get the sparkles".
King said that Bridge and her parents were the only people that she had told about her role in the new line-up.
She added: "I'm very competitive so watch out the other contestants".
"I'm going to be giving it my all".
ISIL training fighters to launch attacks on Europe
It's believed that the Amniyat is now focusing on working with sleeper cells. Then they talk, and when they are ready do the bombings".
Her code name for the top-secret rehearsal was Clio, in keeping with the Greek muses theme for the roll call, and the band member actually only told one person in her Whatsapp group before the grand reveal.
So far, Mollie is the only confirmed contestant for the 15th series of the programme, which returns in the autumn.
There's also X Factor victor Alexandra Burke, Paralympian Ellie Simmonds, Robot Wars host Angela Scanlon, Bros singer Matt Goss, comic Joel Dommett and marathon runner Paula Radcliffe.
Mollie also revealed that she was approached to do the show.
The 55-year-old comedian is reportedly set to star in the upcoming series of the BBC One ballroom and latin show and producers hope he will bring some humour to proceedings.
"Producers loved the sex appeal and performance skills of Daisy Lowe previous year and believe Mollie offers the same". She also released a solo album in 2016.