Have you felt the egg by inserting a finger into her vent? Is she able to poop? How old is she? It could be possible that you are feeling a lash egg, which is a mass of egg matter from internal laying. Those can be small or very large. Shell-less eggs are hard to pass, so that could be the problem. If you are positive she is egg bound, I would seek a vet. They can vaccum the egg out without breaking the hard shell and risking damage to the vent. If you have to attempt this yourself, make sure that you get all of the egg contents and shell out.
Egg binding may occur because of previous vent damage, too large of an egg, dehydration, and a lack of calcium. Tums, Rolaids, human calcium tablets, and crushed egg shells are food sources of calcium. Give plenty of water. Placing the hen in a warm moist environment may help in passing the egg.
