I'm far from a chicken expert and those on here who have been in the 'chicken business' longer than me can give you more information, but I've always read and heard that chickens are very social animals and they need another chicken to be happy. I have four BA's and I know that where one goes, the other three follow. Seldom are they apart. If I had to guess, I would think your hen is lonely and depressed.I have one BR pullet - started with three and gave two to my friend. Now my Opal appears depressed. She stays in the nesting box mist of day. Comes out to eat. She hadn't laid an egg and it gas been almost a week. She was the head pullet and very loud. Now she is quiet. She did have an altercation with a mean crow the day after I gave her friends away. Is she lonely? It having trouble laying? Or sick? She is a about 6 months old.