The pair has worked together for several years, but romance blossomed while they shot the latest installment Harry Potter and the Half-Blood Prince last year (08).
Twenty one-year-old Felton - who plays Harry Potter's nemesis Draco Malfoy in the movies - tells Star magazine, "She's worked on the last few films, but it was only during the last one that I really opened my eyes.
"It's kind of cool when your partner works in the same place.".