Does her breath smell sour?
You may want to take a look at the following articles, she may have sour crop which can be treated by several different methods.
http://www.the-chicken-chick.com/2014/06/chicken-anatomy-crop-impacted-crop-sour.html...
Welcome to BYC.
A few questions...
Can you post a photo of the poo and of her?
Any swelling of the abdomen, hard, soft, swollen?
How does her crop feel, is it emptying?
Has she been wormed?
You are doing what most of us would recommend doing, separating her, giving electrolytes, making sure...