The One Direction singer confirmed on Friday (January 27) that his relationship with the Xtra Factor host had come to an end, allegedly so he could concentrate on the band's burgeoning US career.
"This was a mutual decision. She is one of the kindest, sweetest people I know," he wrote on Twitter. "Please respect that."
It has now been claimed in the Daily Star Sunday that Flack was seen chatting to Essex at the National Television Awards in London on Wednesday (January 25) and the pair apparently swapped numbers.
Essex, 21, was believed to be seeing TOWIE co-star Jessica Wright after the two shared a kiss in the show's series three finale late last year.
He previously dated fellow cast member Sam Faiers for four months. The model claimed following their split in July that she had been "pushed" into the relationship.
Flack's short-lived romance with Styles, 17, was heavily criticised due to their 15-year age gap.
The Only Way Is Essex series four premieres tonight (January 29) at 10pm on ITV2.