Laura is thirty-five years old and recently married to Nick. We don't get to know her much because she doesn't say much, and Nick isn't interested in describing her. He's too busy with Mel.
For much of the story, Laura seems like the anchor in the conversation—asking pointed questions to get Mel back to the story, and throwing in a comment here and there, when the occasion calls for it. But overall, she's reserved, and doesn't take sides in the Great Mel Versus Terri Love Debate of 1981.
With Laura, it's the little things that count. She returns Nick's physical affections, and seems, with her small gestures here and there, to be happy in love. And in a Carver story, that's sayin' something.