Darjeeling (who weighs 15 grams) was poked and prodded by the vet, and given a clean bill of health. No signs that the egg had broken inside, no other worrisome symptoms. Big relief. We had another discussion about calcium. I'm going to start sprinkling supplements (grated cuttlebone, etc.) on their soaked seed, and see if that helps. The vet often suggests that people change the environment of a hen who keeps laying eggs; moving perches around can get her out of the laying mode. But Darjeeling is a Society finch, after all: in my experience it's impossible to get them to stop trying to breed. Moving things around in the Finsterium will never do the trick, the only option would be to separate the males from the females, and I don't have space for that. I took Darjeeling back home and popped her into the Finsterium, where she spent most of the day resting.