Tulisa, who also performed at the two-day festival, posted the above image accompanied by the tweet: "With @NiallOfficial @carolineflack1 and @GarethVarey in disguise in the crowd! Me n Nial pretending 2b chez n Tom from Sheffield ha #VFest."
The X Factor judge's PA Gareth Varey also put photos up on his Twitter page, showing the stars pouting and mock-kissing at the annual music event in Chelmsford.
Varey added: "Festing with @carolineflack1 @NiallOfficial."
Flack, 32, recently responded to a "hurtful" article written about her in a One Direction fan magazine, and has also again defended her relationship with 1D's Harry Styles, 18, in a new interview.