Have you seen this, maybe some of the items may match up with your girl, http://www.merckmanuals.com/vet/poultry/disorders_of_the_reproductive_system/cystic_right_oviduct_in_poultry.html
Sorry not much help then, seems like i had read about something similar on here before and it was a reproductive problem with the hen. Maybe someone else will chime in.
Good Luck with her..