The mum-of-two appeared on the sixth series of the ITV talent show alongside Olly, where she finished in third place and he was runner-up.
Olly is returning to the show this year as co-host alongside Caroline Flack and his old friend Stacey will be supporting him all the way.
Speaking on today's ITV's Lorraine, she said: "He's just such a lovely guy and everything he does he puts everything into it and I really care about him. I'm so glad.
"He is just a really wicked guy and all the way through the show he was kind of like my brother. He's just so much like me and we had such a laugh he deserves everything he gets."
Stacey said she always watches each series of X Factor, explaining: "I think it's the best show for people that might not have had an opportunity anywhere else to sing or to start a career and I think that the show and Simon [Cowell] do so much for people who aspire to be something that they might not necessarily be able to be without it.
"How does anybody meet with record labels? How does anyone get in the studio when you're somebody who doesn't know anyone in the industry? It's so hard just to break through and I think the show really helps people do that and I love it."
Like Olly, Stacey, 25, is one of the show's biggest success stories. After finishing in third place, she went on to win the nation's hearts all over again in I'm A Celebrity… Get Me Out Of Here!, winning the tenth series.
She's voiced a charcter in The SpongeBob Movie: Sponge Out Of Water, written a book called Walk On By, appeared on The Jump and released an album called Shy.
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