The 16-year-old singer from Gravesend, Kent, made her first appearance on last night's show as part of a duo, called Silver Rock, with 22-year-old Jerrie Dila but the judges decided to split them up and make them both perform solo in front of thousands of fans at Wembley Arena.
The teenager, who admitted she was "so, so, so nervous", dashed off stage to her family after forgetting the words to her version of Whitney Houston's I Have Nothing and needed a reminder from show host Dermot O'Leary before going back on and wowing the crowd.
Judge Gary Barlow told her she had "potential beyond belief", while Louis Walsh said she could be better than Leona Lewis and Alexandra Burke - two of the show's previous stars.
The star quit the panel to work on his US version of the show and has not been a judge for the past two years but in an interview with Hello! magazine he promised he would be coming back.
Cowell, who will be back on screens next month with the return of Britain's Got Talent, said: "I'm definitely getting more involved and will have a role in the next series.
"I'm not going to lie - I do miss doing it, because it's like my baby.
"It's been difficult the last two years not being on the show as I always had a great time and the last time that I did do it, it was such a brilliant year. So at some point of course I'm going to come back and do the show."
Swindon's Jahmene Douglas will go head to head with James Arthur in tonight's final of the X Factor after Christopher Maloney was voted out of the competition.
Prior to the contest he patrolled the aisles of Asda in Swindon, marking down products as they neared their best-before limit, but viewers clearly don't think he's reached his sell-by date.
In just a few hours time Wiltshire's Jahmene Douglas will be taking to the stage for the 3rd week of live shows on the X Factor.
Jahmene, who's from Swindon, says he's ready for the club classics theme this weekend - and colourful character Rylan Clark from Essex says it'll be hard to outshine last week's performance.
A 14-year-old boy has pleaded not guilty to the manslaughter of a former X
Factor star's best friend in East Sussex. The teenager, who cannot be named for legal reasons, is accused of punching Connor Saunders of Woodingdean in Brighton last month.
The 19 year old died in hospital. Singer Frankie Cocozza was one of the pallbearers at his friend's funeral. The youngster will appear in court again in October.