Thanks for the advice. Her abdomen feels fine, I think. Soft and and squashy, not firm like a basketball (like with ascites). I did think she might have some sort of fatty liver disorder, she is a big hen and the symptoms seemed consistent. I just didn't expect her to sink so fast. She's really out of it now, i've put a warming wheat filled cushion under her chest (not in direct contact) to try and help comfort her. :/
I'm very sorry she is declining further. You may be correct about fatty liver, since the yellowing of the comb.
A warming cushion sounds very nice. I wish I had better answers for you.
If you happen to lose her and want a more definitive answer, refrigerate her body and send it to your state lab for necropsy/testing. Some of us perform our own informal investigation, looking into the abdomen and at internal organs. If that is something you wish to do, you can post photos here on your thread or on the necropsy thread. I understand, it sounds morbid, but actually seeing what was going on inside is an educational experience, but not for everyone.