Monica - who was a wildcard for this year's competition - was voted off the show after a sing off against Anton Stephans (and a slip up by Olly Murs), but she received criticism for her behaviour on stage as she learned she was going home.
Caroline Flack had asked Monica how she felt about leaving the rest of the contestants behind, to which Monica replied: "Class of 2015 X Factor! Bang bang bang."
Some viewers took to social media, deeming Monica's comments and hand gestures as insensitive.
Taking to Twitter straight after the show, Monica said: "I want to apologise for any offence caused on the @TheXFactor tonight. I wasn't thinking beyond the moment & it was insensitive, sorry."
I want to apologise for any offence caused on the @TheXFactor tonight. I wasn't thinking beyond the moment & it was insensitive, sorry.— Monica Michael (@monicamichaeluk) November 15, 2015
Monica was one of two acts who had to change their song for movie week following Friday night's shocking terror attacks in Paris.
She was originally set to sing 'Bang Bang (My Baby Shot Me Down)', but her last minute change of song saw her perform 'What Is Love '. Lauren Murray also had to change songs from 'Licence To Kill' to 'One Last Time'.
Celebrities, politicians and sports personalities took to Twitter to offer their thoughts and prayers following the terror attack on Friday, which has left more than 100 people dead and more than 40 in critical condition.
Simon Cowell said at the start of Saturday's live show: "In light of what happened in Paris we'd like to send out thoughts and out prayers to everyone who was affected in Paris, last night. And most importantly, please stay safe."