Just an update for anyone watching. After a few days of separation, Big Red has been reintroduced to the flock. I set her out yesterday afternoon to scrounge from the ground and see how she acted. She went right back to how she had been before any illness, back as queen of the roost. She was scratching and eating normally and drinking plenty of water. I thought about pulling her out of the flock again for the evening but she put herself into the coop at dusk, something she wasn't capable of doing herself a few days ago. Optimistic about her future!