My 5 year old daughter is complain about headaches could it be sinus?

Maybe: The label is vague. Yes the sinuses are a structure in the head that can trigger a headache. It can also be one of many other issues from a simple HA to early meningitis. Without more detail (location,intensity,other symptoms,etc.) little can be offered as an answer beyond affirming that it could be.

Nasal saline: An inbox consultation may provide information for you and your pediatrician. In general, if she has thick nasal discharge for a prolonged time period or acutely with fever, this may represent a sinus infection. Rinse nasal passages, obtain routine vaccination and the influenza vaccination and please see your Pediatrician.