If having an active social life is why she missed out, then she is better off having missed out.
Would you hire her?
Also, you're surrounded by a bunch of other interns your age, and the whole program is structured around socializing with them. Years ago, when I interned there, pretty much every weekend there was a different company-sanctioned intern event (hike Mt. Rainier, dinner, movie, go to Woodland Park zoo, concert, etc.).
Women tend to put much more emphasis on these social parts, and its likely even more pronounced considering that this part is probably the only thing that she feels good about.. even now after the final experience.