We have a flock of six chickens who are all 1.5 years old. One chicken—a small and timid barred rock with a bad claw—has always been at the bottom of the flock's pecking order. We've always kept a close eye on her, and the bullying never resulted in a bloody injury, so we did not intervene. We are not sure who is the main bully. One chicken has always been fierce and early on she was definitely high on the social ladder, but recently I have noticed another chicken has been the main one to go after the barred rock when she tried to get some food. Recently, it has appeared that the bullying has escalated. She has been excluded from their perch at night (sleeping in he nesting box while the others perch in the coop) and would always be up in the coop when we went to check on them. When she hears us come in, she peaks her head out and timidly thinks about joining the other chickens in the run because we were there to protect her. Early this cold morning when I went to check on them, I found her at the bottom of their ramp into the run. She had spent the night out in the cold! Worried about her well-being and warmth, we hastily decided to bring her into our basement to keep her warm. It's going to be very cold (below zero to low teens) for the rest of the week, and we are worried and unsure about what to do next. Should we keep her in for a few days? Try to isolate the bully or bullies for a few days? Try to reintegrate her into the flock? Could she be broody? Any help or thoughts would be appreciated.