It's very possible something has started growing that she has a slight allergy to. My Gemma sneezes when we first go into the fields in the morning lately because everything is coming up and it's dewy as well. She also did this during pollen season, but seldom any other time. Of course our A/C is always on because the days are so hot now, and that may be the answer for you. If she had something up her nose, I think she would be "blowing" trying to get it out, but a vet visit would answer that for you.