"Alex might see himself as a bad boy, but he's actually very sweet in real life," she tells the mag of her British beau, 20. "And I think it's important to have your differences in any relationship. I wouldn't want to be dating a carbon copy of myself. That would just be boring."
So who's responsible for introducing the couple, who costar in the upcoming sci-fi flick I Am Number Four?
"The film's director [D.J. Caruso] basically set us up. He was like, 'Maybe you should meet this guy before you're forced together in front of the cameras,'" Agron explains of Pettyfer, who once dated Emma Roberts.PHOTOS: Celebs who found love on set
"So Alex and I met for dinner, and I was really worried that it was going to be awkward, so I brought along my dog to break the ice," Agron continues. "Within minutes this huge German Shepherd was up in Alex's lap, licking his face. It was so funny!"