Former X Factor star Rebecca watched the show on Sunday night (12 October) and saw Stephanie face the sing-off with Overload Generation.
It was a difficult first week for Stephanie, who had failed to impress the judges the night before with her performance of 'Everything I Own'.
Simon Cowell said he thought Stephanie was more suited to being in a girl group, explaining that he thought she lacked the "confidence" to be a solo singer.
Meanwhile, Louis Walsh added: "The song was flat. You look amazing but you sounded awful."
The 20-year-old, who is being mentored by Cheryl Fernandez-Versini, was then forced to fight for her place along with Overload Generation in the sing-off on Sunday.
But with the judges' decision split, the vote went to deadlock and Dermot O'Leary revealed Overload Generation had the fewest votes, so Stephanie would be safe for another week.
Pregnant X Factor star Rebecca, who was runner-up on the show's seventh series in 2010, tweeted last night: "@StephanieNala you need to prove doubters wrong! And tap into what makes you unique because you are beautiful and talented!
"Some of them look good but wouldn't sound good on an album! Recognise your difference! And believe girl you're fab xxx."
Stephanie simply retweeted Rebecca's message and replied: "@RebeccaFMusic you're literally someone I would love to be like! You are amazing. Means so much coming from you."
Rebecca wasn't the only celeb to tweet support, as 1D's Louis also said last night: "Hope Stephanie gets through! She's got potential! #XFactor."
Stephanie was previously in a band called the Luminites, who rose to fame after reaching the live shows of Britain's Got Talent in 2013.
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Watch Stephanie's sing-off performance below: