What could possibly have an 8 year old child have anxiety. i can see getting it when she was in a play. however, she gets it for no reason & says she is going to throw up. she doesn't even know why she gets like this?

No untrained adult can ever appreciate the stresses of a child of almost any age. Get the kid screened by her doc and arrange for her to work with a child psychologist. While the kid learns skills to relax they can discover the issues that lead to her stress. It is often something that would be simple to an adult, but not to a kid. Get the help while the kid can still be helped.