Sounds like the opening line to a bad joke. The vet said it was probably a prolapsed something or other which means it had a tried to lay an egg that probably had a very soft or no shell. This would have made it almost impossible to lay and it tried so hard it expelled its reproductive organs - and that is exactly what it looked like.
Teresa told the children while I was at the vets, Emily had a little cry but thats okay. We told them that Bertha was dead had died no saying she had gone away or chicken heaven because that is not what happened and would only cause problems in the future and Emily is always asking about dying.