Twitching of the head could be a neurological symptom. What breed is she and how old is she?
Check her over for any lice and mites. Look in the ears for any dirt/debris or infection.
What type of food/treats do you feed?
How did you treat the respiratory illness?
It's hard to know what exactly is going on with her - as mentioned in the previous post, sneezing can be cause by environment, but if it's accompanied by nasal discharge, then most likely you have a respiratory illness. Infectious Bronchitis and Mycoplasma symptoms can linger for months, even with treatment.
The only thing I can suggest, without more information (photos and video are always welcome) is to make sure she is eating/drinking well. Keep the nostrils cleared of any discharge you see. Offer poultry vitamins that include Vitamin E and B1 along with some chopped egg for Selenium. (this is in addition to her normal, balanced poultry feed).
If you are dealing with a contagious respiratory illness, there is no "preventative" except to make sure your coop has plenty of ventilation, provide balanced nutrition daily and give your chickens a boost with poultry vitamins once a week.