Could just be something wrong with her throat if she has allergies or something like that. Also could very well be a tic. I would ask your doctor about this. good luck
Constant or repeated throat clearing in a child can be a habit he/she may have picked up from somewhere. It can also be due to post nasal drip (if the child has recurrent upper respiratory infection/sinusitis etc) or due to gastric reflux. It can also be a vocal tic. Seasonal allergies can irritate the throat and cause the urge to clear the throat. Please show your child to an ENT specialist and pediatrician. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.