I'm going through the exact same thing with my leghorn as well... one thing that I found helped was to hold her head down and massage her crop if its impacted or sour, especially if she has been drinking a lot of water.
Hope your girl gets better!
I trained my doberman to accept my chickens (this is a dog that will kill anything smaller then him on sight - groundhogs, snakes, squirrels, opossums, cats, etc. not to mention he's caught birds mid air). I started with introducing him to the chicks and correcting him if he got too pushy trying...