Why did Mrs Robinson ask Benjamin not to take Elaine out in The Graduate?

It would be easy to just say it was jealousy, but that would miss out on the complexity of Mrs. Robinson and her place in feminine history. In an insightful article written for the Berkeley Undergraduate Journal, Rebecca Neumann traces how Mrs. Robinson has evolved into the "cougar" of recent times. She notes how difficult it is for people in recent generations to appreciate the experience of a middle-aged woman in the 60s. She also notes the care with which director Mike Nichols and writer Buck Henry crafted the character of Mrs. Robinson through details in the film.

Some points she makes:

• Mrs. Robinson is a predator - she is often dressed in animal prints.


• She is not motherly - she never shares a scene alone with her
  daughter.


• She is vengeful toward her daughter whom she is jealous of for
  attending college - she seduces Benjamin in Elaine's bedroom even
  though she knows Elaine has a crush on Benjamin.


• The affair, which is about power more than anything else, hurts her
  husband, whom she also holds responsible for her powerless situation
  because of the unplanned pregnancy that caused her to drop out of
  college.


• Her powerlessness is also demonstrated in her financial dependence on
  her husband, her inability to drive, and the fact that the only name by which
  she is referred is her husband's name.

"The particular social order that produces The Graduate's Mrs. Robinson is specific to the 1960s." This bored, bitter woman was pre-sexual revolution, pre-birth control, pre-abortion, pre-women in the workforce after marriage, pre- no fault divorce. Mrs. Robinson was a woman with no choices, no outlets except this affair. It was a passionless affair of which Benjamin says they "might as well have been shaking hands." It was an attempt to have power over one corner of her life, a power she wielded over Benjamin, and in order to maintain that power, she naturally could not allow Benjamin to date her daughter.

Predator, Prisoner, and Role Model: The Evolving Figure of Mrs. Robinson, 2011