This sounds like very, very common scenarios, being the person that is now the small fish in the big sea when they had been the big fish in a small sea is unsettling, plus she also is moving from an established social hierarchy she had in middle and high school, kids she went to school likely for years, to someplace where she is entirely a face in the crowd.
I agree with others, as a parent we can only be supportive and a sympathetic ear, we cant’ change anything. One of the things the D or any child has to recognize is that in a big school like that (I went to a big private university), what I found was that you end up finding a smaller village in the big city (and I apologize for the cliche, I don’t like them much, but seemed to fit). She is going to need to go out of her comfort zone to find new things, if the old things didn’t work. She also has to realize that the pool being so large, it is likely she won’t be the best. This is common with music students, when they hit music school/conservatory, they may be for the first time seeing kids who are well advanced of where they are (and even if you have experienced it, as my S did being in a very competitive pre college program, it can be daunting). I would tell her that if she made the dance team, it was for a reason, and that if she isn’t the best, that is great because it is a challenge to meet, much the same way that the amazingly accomplished kids in my S’s studio help drive him forward.
I also think others are right, that if she is keeping up with other kids she knew on facebook or whatnot, it likely looks like they are having the time of their life…without realizing their parents are probably hearing the same thing (I would tell her that, or tell her what other parents have said to you, either on here or IRL). Back when I went to college, when we used chisels on stone tablets and all that, you went away to school, and really only saw friends from high school when you went home for holidays and such, so by the time we saw each other, most of us had found our feet, and could complain about the really important things, how bad the cafeteria was, the teacher from hell who wrote equations with one hand and erased with another, the dating scene (never the lack thereof), etc, etc:)