First I suggest you check she is not egg bound. You need to thoroughly wash your hands and grease your forefinger with coconut oil or even Vasaline and insert it into her vent.
You can gently slide your finger in up to the second knuckle. If hse is egg bound you will be able to feel the egg.
I would guess from your description that an internal laying problem is more likely. Lack of appetite and crop problems are often symptoms of peritonitis, or other reproductive tract problem.
You can tube or syringe feed her in order to test her crop function. Here is an article on how to do this.
https://www.backyardchickens.com/ar...dications-to-all-poultry-and-waterfowl.73335/
If you feed her during the day and her crop is full at night, then if the crop is empty again the next morning the crop is functioning.
If she does have reproductive issues I'm afraid there isn't much you can do. It's a question of keeping her hydrated and fed until the point comes when her quality of life is poor and then the kindest thing to do is to kill the hen.
I'm sorry to not have more optimistic advice.