Princess Fiona is recovering nicely. She managed to hobble upstairs into the nesting box yesterday to lay an egg. We didn't see her do it but at the end of the day there were four eggs, one from each chook!
Given she stayed seated most of yesterday, Erin granted her an extra night in the caravan (as it didn't seem she was quite ready to perch with the other birds). The extra rest did the trick - our Princess is now standing up and limping about a lot more readily.