Incorrect Synopsis of This Film on IFC?

I saw this film recently on IFC, and I think their synopsis of the movie is not quite correct. It says, "A stern writer's affection-craving husband finds comfort in the arms of his wife's younger sister."
It seemed to me that it was the wife who is starved for affection, not the other way around. At the beginning of the movie, she wants to make love to her husband but he refuses; later it is revealed that he is having an affair with a younger woman. Is it Beth's strong feminist beliefs that make her European husband insecure and unable to love her? It seemed to me that she loved him very much.

"I have been one acquainted with the night..."
(Robert Frost)