Sharon, who was a judge on the first four series of X Factor, was previously thought to have been blacklisted from the show after she publicly spoke out about Cowell at the start of the year.
The reality TV star mocked Cowell's penis size and was critical of comments he made about her in his unauthorised biography The Intimate Life Of Simon Cowell.
However, Sharon and Cowell have been in contact since her son Jack Osbourne was diagnosed with multiple sclerosis, and the pair have patched up their differences.
"We're like brother and sister. We row, then we make up. We love each other, then we fight, then we love each other, then we fight," she said.
"But you know, one of the first people to reach out to me when Jack was diagnosed with MS was Simon. And that meant very much to me. Because it meant maybe he loves me, just a little bit."
Sharon will appear at Louis Walsh's Judges' Houses in Las Vegas. It is the first time she's appeared on the show since 2010, when she made a cameo at the same stage of the competition.
Speaking about Jack's battle with MS, Sharon said that her son was "determined not to let this stop the way he lives his life".
Commenting on how it has affected her life, she added: "You go through the guilt, you go through the, 'Is it me, was it me?', and you go through the family tree going, 'Who died of what? Where did this come from?'
"I've become even more of a control freak. I think I'm driving him nuts. He's got a headache and I'm all like, 'Go to the doctors! I'll drive you myself!' And I'm fussing and asking him what he's eating and all of that kind of thing.
"He's as good as married and he has a baby, and he left home about a hundred years ago, and I'm still fussing over him. I think I'm driving him mad. But that's what mothers are for."
The X Factor continues on Saturdays on ITV1.