The Xtra Factor host was spotted kissing the singer, 14 years her junior, last month after he apparently romanced her.
"They had a big passionate snog and it caused mild hysterics with the group of people they were with," a source claimed at the time.
A supposed friend has now told Heat: "It was just a drunken snog and nothing else. She's been trying to forget about it."
Styles has said that Flack is "hot" and one of his favourite women.
The One Direction star had previously said that he likes "a babe with a talent", adding: "If Caroline Flack is reading this, say 'Hi' from me. She is gorgeous!"
When quizzed about the kiss, Styles later said: "It was a bit misconstrued... it wasn't like that."
Watch Harry Styles talk about kissing Caroline Flack below: