Quoting the report:
E! News has learned that the casual-maybe-couple have called it quits, however, a source reiterates that the duo were never really in a full-fledged relationship, telling us, "They were never officially together, but more casual hanging out and having fun."
So what caused the flame to fizzle? One source tells E! News, "It was super-hot and heavy, and because Justin doesn't want a relationship right now, he wanted to cool things down," but adds that "it wasn't an intentional cool-off," and it "just sort of happened on its own."