I have no idea!! Poor baby. I don't blame you for not wanting to give up on her. Living her whole life in a shelter is really sad. She must be a very emotional kitty.
I have heard others here on PT talk about baby food and yogurt. They act like the cats really like it. With everything you have already tried I doubt her reaction woud be any different. Does she respond at all to nip? I know most of my cats eat the heck out of it. Maybe if she does like to eat it then you could sprinkle some on her food. Other than that I would be at a loss too.
I know one time when one of mine was sick the doctor gave me some kind of liquid vitamins and he said it would also encourage my guy to eat. I don't have any idea what it was because it was some years ago. Maybe there is something that the vets have that could help.
I know one thing that works wonders...PT PRAYERS!! She will be getting prayers from me. Don't give up yet Jen. If anybody can do it it will be you! Please keep us posted.
What is her name?