Adjusting to high school is a big deal. Most of us can remember how it felt to enter the "big time." It requires a great deal of social skill and adaptational capacity. My suggestion is to talk to your daughter's guidance counselor at school. You might explore what can be done to help through the programs and social groups that the school has for incoming students. In fact, some schools have "adjustment counselors" who can help with this type of problem.
Another option, if this one is not successful, is to seek outside professional help from a social worker or psychologist who is familiar with school adjustment issues.
Of course, whatever you do, do find time to talk to your daughter and see what is going on. Sometimes there are interpersonal issues or stressors outside of school that affect school adjustment. Your gentle questioning may help to alleviate her anxiety. You can reassure her that some nervousness is normal and that she will get through it.
Be sure to check to see if she can handle the academic load. There are many potential stressors as a new highs school student that can affect her adjustment.
Good luck and let us know how she is doing.
Bette J. Freedson, LICSW, LCSW, CGP