Thanks for your feedback - we only have 1 other hen so we haven't seperated them, We didn't check for swelling - she seems to be walking a bit better but still with a limp.
Hope someone can help - my hen was attacked by a dog we think as she had wet feathers but no blood or puncture wounds that we could see. I kept her comfortable in her nesting box and lifted her in and out for fresh air - she is eating and drinking okay - she can now stand up and seem to clean...