I read recently where up to 30% of hens over 2 get reproductive cancer. Many others get salpingitis, and lash egg material may be seen inside the abdomen. If reproductive infection is treated early with antibiotics, it could possibly help, but it may not. There probably is not much you can do except provide supportive care, let her eat a healthy diet and hang with her flock. If any of mine ever seem to be suffering or they get pecked or shunned by other chickens, then I will consider putting them down. It can be helpful then to do a simple necropsy of the abdominal organs to look for anything unusual.