The WJ-IV has age norms beginning from age 2 through 90+. So she will be compared against a nationally-representative group of her age peers. However, she will not have scores in every test or composite possible, and many of the scores she can obtain will be less reliable, for the reason you mention (that very few children her age are reading, writing, calculating, etc.).

...pronounced like the long vowel and first letter of the alphabet...