She may have a disorder called Pica. This can be dangerous because of what she chews on and internally what can happen to her. I would switch to a better type of food for her, something that is a bit meatier with less filler. Remember a cat's primary food are rodents. www.miceonice.com is also a possibility.  The problem with Pica is that not that much is known about it, or how to treat it. There is one school of thought that believes it is a chemical imbalance and another that believes it is food-related. It is not uncommon and I believe there is even a yahoo group that you can join that brings cat owners together whose cats are suffering from this.  I had one cat long ago that had it, and she used to eat my husband's socks. I found that by giving her two mice a day it stopped her from wanting to eat unhealthier items.