L.S.
If there is a problem at any age it is appropriate to adress it.
Good grooming habits are developed early. It is important for her overall health that she understand how to keep that area down below clean and excess hair can be a problem for some women.
If hair protrudes past the lines of her bathing suit or creates a visable buldge it is a social norm to remove or reduce that hair.
If you or she is nervous about the using the razor in that area you can try the buffing pads they have recently been advertising on TV, smooth away I think they are called, my sister uses them and loves them.
My mother shaved my under arms at 6 because I was so embarassed I refused to leave the house in anything sleevless.
Hope this was helpful,
L. in Metairie