I wonder is she has a liver issue, such as cancer or fatty liver hemorrhagic disease? Her urates are bright yellow which means liver problems usually. Water belly is usually present with liver disease. Vitamins or dehydration might add to that. Your vet did a thorough check and I feel that you may not know exactly what is going on until she dies and a necropsy can be done. If you are in California, UC Davis (at 4 locations) does them at a very low cost. That is about the only way we can solve the mysteries of an illness. It is amazing that she is still walking around after all of the blood loss. We have a lot of glass shards in our soil where people on our farm would carelessly throw things out. I have spent years picking up small pieces so that my chickens don’t eat it. Glass does not show up on xray usually. Please let us know how your hen gets along, and if you find out the cause.