Women's sexual desire (and men's, too) is far from simple -- it is more like a complicated puzzle, the pieces of which the pieces we are still trying to put together. Having pervasive sex-negative myths isn't helping anyone.
This is the first movie since It's Complicated that portrays sexual relationships in folks past 40. It bravely tackles the complex issues of sexual desire and intimacy in "seniors," however we may define that term.
It's no longer true that men cheat far more often than women do. A study conducted last year by researchers at Indiana University in Bloomington found that women and men cheat at about the same rate -- though for different reasons.