She's still enjoying life - roaming round the garden, flapping her wings, eating well, generally bright and alert.
We've established a routine now whereby she spends the days in her half of the run, having supervised time out roaming with my other hen who was pecking the swelling and adding to the problem by causing wounds. The two of them spend these cold winter nights in the kitchen inside in their own boxes.
Unfortunately the swelling is getting larger. I don't think it will be long before her quality of life deteriorates.