Hannah, who is part of Nicole's girls category in the current series, landed in the bottom two alongside Gary Barlow's group Miss Dynamix following their Movie Week performances.
After the sing off, the judges chose to send home Miss Dynamix – a move which X Factor creator Simon Cowell thinks was wrong. He tweeted after the Sunday night (27 October) results show: "I would have kept Miss Dynamix. I don't get that decision."
Feisty Nicole, however, has come back fighting, defending her act in a Twitter post this afternoon.
Nicole wrote: "I have never had a Twitter war, please don't make me start one now Simon Cowell. You R crazy, my girl Hannah is a STAR… and with soul!"
The former Pussycat Doll also retweeted a fan who wrote on Twitter: "You tell him girl! Hannah is schmazing!"
Simon has yet to respond. He left the UK X Factor judging panel to launch the US version of the show but is still heavily involved in the British programme behind the scenes.
Hannah's place in the bottom two was a shock to the judges and the viewers as her rendition of Adele's 'Skyfall' on Saturday night had been praised by the panel.
Gary suggested during the results show that viewers assumed Hannah would be safe as she was so good, a sentiment echoed by a still stunned-looking Nicole on Xtra Factor.
She has since urged fans not to presume Hannah is OK next week, tweeting: "Pls make sure to vote for @HannahBMusic on @TheXFactor She is the truth! "A Phoenix rising from the ashes"."
Hannah. meanwhile, is eager not to have to repeat the tense sing off next week, telling fans this morning: "Thank you for all the love and support! Last night was horrible I just hope this week will be a breakthrough love you all."
Watch Hannah's save me song from Sunday night below: