You've pretty much described a collapsed egg or her body's attempt at an egg, and it would be the correct size for that.
It also matches up with her lethargic behavior. She may still have more material in her oviduct that needs to come out. Then she should feel better.
Give her a calcium tablet immediately. This will assist her in strong contractions to expel anything still in her. Then, as @Wyorp Rock has suggested, give her a calcium tablet each day until she is laying normal eggs again.
It also matches up with her lethargic behavior. She may still have more material in her oviduct that needs to come out. Then she should feel better.
Give her a calcium tablet immediately. This will assist her in strong contractions to expel anything still in her. Then, as @Wyorp Rock has suggested, give her a calcium tablet each day until she is laying normal eggs again.