Chronic cold?
perhaps se has a slight allergy to something she eats once in a while. look out for any possible allergy causing things whenever you see her symptoms arising.
Also, if she has a chronic cold you should look into getting her to a doctor who specialises in lung/breathing/nose issues.
or a regular doctor, but get her airways checked!
It's possible it's allergy related - the pollen situation this year is absolutely HORRIBLE!!! Check with your pediatrician about either having your child tested or perhaps trying some mild antihistamine type medication to see if it helps.