The 27-year-old, who first met her boyfriend of a year on the set of her 'You & I' video in 2012, said sparks flew when he spontaneously kissed her, reported Contactmusic.
"And we were in the middle of this scene and I remember that he kissed me and it wasn't scripted for him to kiss me and I was sort of like was um, you know, was that real or was that fake?
"And he didn't really say anything and that was fine by me and we kept filming," she said on 'The Ellen DeGeneres Show'.
"And you know, at the end of the day he's my best friend and having your lover be your best friend. I mean, it's the best thing ever. It's the best thing I can say about it," she added.