Stewart, who attended the duo's surprise wedding in South Carolina earlier this month, explained that they "live around the corner" from her and revealed that they often "hang out".
"[They] are the nicest couple," she told Us Weekly. "And very, very modest and nice, contrary to the parts they play."
The chef also claimed that both Reynolds and Lively looked "very gorgeous" at their wedding.
Wedding planner Tara Guerard, who organised the ceremony, has previously claimed that the nuptials were "truly elegant" with the "charm, elegance and magic of times past".
Meanwhile, rumours have suggested that Lively could be expecting the couple's first child, though neither she nor Reynolds have confirmed the speculation.