The Inbetweeners actress told Reveal she briefly got together with the One Direction star but that it was never an official relationship.
She said: "We had a nice little fling. We were never boyfriend and girlfriend. I think that's the first time I've ever admitted to what it was, because I've always just shrugged it off before."
There were rumours the pair were dating in May last year but neither of them has ever spoken about it before.
Former Dancing On Ice star Emily said: "I think it's best to clear it up. So, yeah, we had a short-lived thing that was just a bit of fun. Then we went off in our different directions.
"Harry and I had a laugh. It was brief, but fun, and then we moved on. We haven't spoken in a while... he's one of the most famous people in the world now."
Little Things singer Harry, 19, has since dated Taylor Swift and been linked to Cara Delevigne, while Emily, 23, is with 19-year-old model Jack Vacher.