If your child is 8 years old perhaps the beginning of school is stirring some anticipation in her. My children get this way each year. School starting is a stressful and exciting time for children. I know that the behavior you described is well within normal for my kids.
Just a guess, I am not a doctor nor do I play one on TV. :) If you are truly concerned you should speak to your physician right away.
Has anyone here had or known a child with panic disorder. My 8 year old daughter is being treated with Prozac for depression. I am recovering from panic disorder and she has never really been exposed to what I have gone through, I am very good at disguising it :O) She was doing very well, but in the last week she has had trouble going to bed again, doesn't want to be alone and is constantly worrying! The symptoms she describes are what I went through myself! HELP!!!