For the past 1-2 weeks, my 6-year-old daughter has been blinking very frequently. i am taking her to an eye doctor in a few days but wanted to ask what could be the cause thanks?

Several causes: Frequent blinking could be due to factors local to the eyes like dryness of eyes, foreign body in the eyes, allergies etc, it could also be due to disorders that cause abnormal involuntary movements arising from the nervous system or could be due to a tic. A visit to the eye doctor is prudent, consider a visit with his pediatrician as well for an assessment of other causes if needed.