What did she major in?
Another story, this time from Stanford: a guy whom I grew up with (he graduated MIT as a physics major) had a son who was also quite brilliant and graduated high school as valedictorian. He went to Stanford and almost dropped out because it was so difficult. He went on to graduate (and is now in medical school) but he had to work his butt off.
While there may be some legacies who get "gentlemen's C's" most kids who go to the Ivies work hard and are--for the most part--the top kids from their high schools. Especially nowadays.