This is just a suggestion, and you may have already tried this, but have you tried one of the metal exercise pens. They run about $50. That way she couldn't chew it up. They come in different sizes, and you could put it in your kitchen so it would be easy to clean up.
I'm not sure how big your exercise pen is now, but if it is a smaller one, maybe a larger exercise pen might help her not to eat her poop because she would have more room.
I have attached a picture of the exercise pen I am talking about. Hope you find a solution to your problem. I know it must be frustrating.
http://thumbs1.ebaystatic.com/m/mrrI...W2bh-w/140.jpg