The term cougar hadn't been invented when Benjamin Braddock drove his father's business partner's slinky, uncommonly self-possessed wife home from a party. If it had, he might have had more of an idea what he was in for. He certainly wouldn't have had to ask his famous question: "Mrs. Robinson, you're trying to seduce me. Aren't you?"
Of course, there's nothing wrong with an older woman seducing a younger man (though in fact Dustin Hoffman, who played Benjamin, was only six years younger than Anne Bancroft, who played Mrs. Robinson). True, she was married at the time — not great. But the knives really come out when Benjamin goes and falls in love with Mrs. Robinson's daughter Elaine.
The gracious thing to do would have been to step aside. Not Mrs. Robinson: she does her level best to ruin Benjamin's, and her daughter's, best chance for happiness in life. Maybe she's bitter because she never gets a first name? Though one person's bad mother is another's post-feminist role model. For a dissenting viewpoint, consult the Mrs. Robinson Society.