R.S.
I agree with Jen C.
You will need to find an agency...send in a couple of good snap shots of her and see if any agencies are interested.
Children typically do not need head shots as they are always changing and would have to be redone every three to six months.
Do not pay out any money...reputable agencies make their money by booking work for you. Not in any other way...they should not sell photos or classes.
If you do get offered representation read the contract carefully and know how you can break it...what their fees are...and so forth and so on.
It is tough and competitive...but good luck.