Can chickens get Bell's palsy?
She could have an eye infection or have been pecked around the eye. You can put Terramycin ointment or Vetericyn eye gel from the feed store, or just put some plain Neosporin or triple antibiotic ointment into her eye twice a day. If you see any pus or crusts, then clean those out with saline and cotton. Look for any foreign body in the eye. If she develops symptoms of a respiratory disease, then putting her on some oxytetracycline in her water for 7 days may be needed, but hopefully, it is just something with her eye. Here is a good link about the common respiratory diseases such as MG and coryza with symptoms: http://edis.ifas.ufl.edu/ps044