Well. I am at my wits end. The snow is melting in patches, so I let my girls out on the weekend. There is a bare patch under a tree near the coop where they all like to do the dust bath thing, and another dry patch, with a little green showing, beside the house. I put Backroom Chicken (BRC) near the house where the green is and let the others out of the run, so they could pick at dried grass and roll around in the dirt under the tree. The two areas are about 10 yards apart and separated by snow that is still 1 - 2 ft deep. I selected a few birds and carried them over the snow to the green space to judge their reactions and let them get used to each other again. BRC was quite the little queen. She was very territorial and attacked all three birds that I brought over, but they soon settled into an uneasy truce and all scratched together in the fresh green grass. When I checked a while later, the three I had brought over were all back under the tree, and BRC was alone in the green patch. I checked again about an hour later, and BRC had actually braved the snow and was enjoying a nice dust bath under the tree with the other birds. 
My plan was working! I had solved the problem... 
I should be so lucky. 
When I went out to tuck them in for the night, BRC was back her original green patch, and the others were all in either the coop or the run. I picked her up and carried her to the coop, where she just sat on a ledge and did not move. I waited for a while to let her settle in and then shooed her down to mingle with the others. She was swarmed immediately. I swear I've never seen a chicken move so fast. She be-lined it out the hatch, across the run, though the open gate, over the snow and straight to the back door of the house, where she impatiently marched back and forth across the porch, waiting for me to catch up. I opened the door, and she went straight to her open cage and hopped right in, like it was where she belonged. 
Sigh... Where can I get chicken diapers? 
I hate randomly stressing her like this. Now that it is warmer, I am going to try keeping the hospital cage in the coop and see where that leads. 
btw: I added some organic ACV to her water, and she does love her parsley, kale, cabbage, strawberries, avacado and grapes, but I haven't had a chance to pick up any clover flowers yet.