Is she still able to poop? If so, then I am pretty sure she is not egg bound and what you are feeling is probably not an egg. When they are egg bound, the egg is usually right inside the cloaca and they are unable to pass faeces which is what causes them to die within a couple of days. The oviduct is located in the upper part of the back end.... see diagram below....
I wonder if you are feeling her gizzard, which is very solid and egg sized.
I wonder if you are feeling her gizzard, which is very solid and egg sized.