The singer made it to mentor Nicole Scherzinger's Judges' House in Antigua, where she gave an emotional performance of Snow Patrol's 'Run' for Nicole and guest judge Mary J.Blige.
Speaking to host Dermot O'Leary after her performance, Melanie said: "I feel like I have done everything I can, but I still feel like I could have done more because that is the type of person I am."
But despite both Nicole and Mary being visibly impressed by Melanie's audition, Nicole decided she could not give her a place in her final three.
Melanie, 20, first auditioned for the X Factor in 2008, when she was just 14, before returning in 2011 and going as far as the Judges' Houses stage, but she was sent home by judge Kelly Rowland.
Melanie decided to try again last year but only managed to get as far as Bootcamp.
While delivering the bad news, Nicole told her she had the "biggest range vocally" of the final six girls in the competition.
She is really giving us everything.
Nicole Scherzinger on Melanie McCabe
"But I still feel like there is lot of work to be done," she added.
"I don't know if you're afraid to connect, because sometimes there is a disconnect, you are trying to be so perfect."
Speaking about her decision to let Melanie go Nicole has admitted that she shed tears over the Dublin singer.
She said: "I knew this was her fourth time on the show and I knew how badly she wanted it.
"Honestly my Judges' Houses was something else. Everyone agreed with me, the whole production team. It was the hardest Judges' Houses in the competition, ever.
"It was Melanie who particularly got to me."
Receiving better news from Nicole was 16-year-old Tamera Foster, who performed a rendition of Mary J. Blige's 'No More Pain'.
But before Nicole gave her a place in her final three she admitted she needed convincing as to why Tamera was in the competition.
"If I'm honest with you I haven't made my decision yet with you because I feel like for whatever reason that we haven't connected," she said.
"I know that you are still so young - but you are here and you have made it this far so it is important for me to hear why you are in."
That's the best I have ever seen her perform.
Nicole Scherzinger on Tamera Foster
Tamera told her;" Music has helped me through so many hard times in my life."
Nicole decided to give Tamera a chance along with supermarket worker Abi Alton and student Hannah Barrett.
Meanwhile the fate of Gary Barlow's Groups were also determined, with the Take That singer deciding to put through boyband Kingsland, newly formed girl group Miss Dynamix and vocal group Rough Copy.
There was a huge choice to be made regarding Rough Copy who initially auditioned for the X Factor as a trio, but was forced to take their place at Judges' Houses as a duo because of visa issues surrounding founding member Kazeem.
Bandmate Joey said performing without Kazeem at Judges' Houses was "crazy weird", adding: "We'll always be a three. It's just that there's two left here to carry the weight. He's relying on us to bring back the good news."
Rough Copy impressed Gary as a duo, but he felt that without their friend it was like "a body with a piece missing" and he vowed to "do everything he could" to bring Kazeem back to the band.
After returning to the UK, Gary surprised Kazeem by turning up at his house with the good news that he was allowed to re-join Rough Copy for the live finals.
The X Factor live shows begin on UTV on Saturday and Sunday from 8pm.