sick hen

[rebrascora]

Her breast bone being sharp suggests that this has been going on for weeks. She will definitely benefit from a heat source.
Has she eaten the boiled eggs and oli soaked bread? Is her crop going down overnight? You need to check it at night when she goes to roost or lights out if she is in a cage) and again first thing in the morning before she has access to food. If it is a crop problem, she will benefit from a crop massage. If it is sour (breath will smell bad) feeding her bread will not help but oil and egg are good. Gently massaging for 10-15 mins up to 4x a day will be beneficial provided she does not protest.... most chickens will enjoy a crop massage when they are having problems. Feed only oily, sloppy food and avoid anything lumpy like grain or fibrous (remove access to hay or straw and maybe even shavings if she shows an interest in eating them.

What does her poop look like?

 

[azygous]

If she isn't eating, I would suspect sour crop and treat with Nystatin or miconazole. If she is drinking mostly water in large amounts, then I would treat for impacted crop first and then do the miconazole for possible yeast.

This treatment would be to make the hen more comfortable as well as rule out these causes for her illness. It might resolve things or not, but it's worth a shot.