The Sunday Mirror's Dean Piper revealed today that the young performer would join the show next week.
The 21-year-old singer has only released a single song in her short career, but hit the top spot with the debut track this month.
Featuring Tinie Tempah, R.I.P. sold over 100,000 copies in its first week.
Former X Factor judge Leona Lewis will join the panel tomorrow (Saturday, May 26) at the first London date.
It's unclear whether or not Rita will also be present for the London dates on Tuesday and Wednesday at the O2 Arena next week.
It's expected that a new fourth judge will join Louis Walsh, Gary Barlow and Tulisa permanently from the bootcamp stages later this year.
The X Factor 2012 will air on ITV1 in August.