Byrne, a supermarket worker from Dublin who has wowed the judges every week with her powerhouse vocals, will be singing "There You'll Be" - a Faith Hill song that was used on the sound track of Pearl Harbour.
Byrne, 50, is one of the favorites to win this years contest and rumors are rampant that judge Simon Cowell has already promised the Dublin lass a $1.4 million record deal when the show is over.
Byrne has been described as the next Susan Boyle.
On the Derek Mooney RTE radio show Byrne said this week's song is a "new ballad, not an old ballad."
"It’s beautiful song and it’s very touching. That’s all I can say. If I can put it across the way I put across my old ballads the whole of Ireland and myself will be crying."
When another guest on the show guessed the Faith Hill song, Byrne said "Yes."
And Byrne admitted another little secret.
She said, "I feel fantastic. I really do. I’ve been losing weight. I’ve lost nearly a whole dress size."
Joking about the young people she shares the contest home Byrne said "They are great kids and I love living there.
"Louis just thought I wasn’t getting enough rest so he decided if I wasn’t getting enough rest he was going to put me in a hotel room, but I thought that would be very, very boring so I decided to stay where I am."