Yes, we've been there.
Chill, open her mail. This often reflects some ambivalence about the transition.
Remember, if you went to college and had a great experience, which many of us did, you look at this summer as the prelude to some of the best years of her life. She can only see this as a BIG change, which may mean losing many friends.
Just be certain she doesn't miss any deadlines that are important to life, limb, money and graduating on time, and she will be fine.