Normally I wouldn't separate a chicken from the flock to avoid reintegration issues, but you might want to try and shock her a bit by moving her somewhere else (a garage, basement, etc) for a day or two (which shouldn't be long enough to let the flock completely forget her) and seeing if that helps break her.Any suggestions I don't want to see her needing to stay in this cage much longer but letting her out seems to return her to the nesting box even if it's not right away.