"He's your dream costar," Mendes, 37, tells Marie Claire in its March issue. "I have never felt so creatively satisfied on a film. He's amazing."
But that's about as much as the notably private actress would reveal about Gosling, 31, who Mendes was first photographed holding hands with in September.
"Stop, just stop," she told the magazine's reporter with a laugh when he attempted to begin a follow-up question about her beau. "I'm not gonna budge. I feel uncomfortable talking about it. It's too personal."
Courtesy Marie Claire
That's not the only subject off limits for Mendes. She also refused to address the possibility of getting married or becoming a mom at some point (not necessarily relating to Gosling).
"Those are such boring topics to me," she says. "I am not that girl. I don't like talking about things that I want in the future because I feel by verbalizing such things, they won't come true."