L.D.
Not necessarily. Some kids are more sensitive than others. Has she always been the anxious/sensitive type or is this something new? Do you have a sense of what's causing the anxiety?
Is she getting along well with everyone at school? How are things going at home? Maybe there's something in particular that is stressing her out and she needs to work it out and get better ways to learn now to manage her stress instead of internalizing it.
How's her health? If she is eating a lot of processed food and consuming a lot of sugar, that will effect her nutritional health and excess sugar can cause an excess of bad bacteria in the intestines -- a condition called candida -- one of the symptoms of which is anxiety. If you are seeing digestion issues as well with her, this may be something you will want to do more research on. The book Gut Solutions is a great resource if information.
Hope this helps and I hope she feels better soon.