OR, What if he feared that her body would be examined/autopsied and reveal evidence of molestation on his part?
Right there is reason enough for him to leave the body up there and let it rot and dry out, and concoct some explanation that would make it look like somebody else may have molested, if worst came to worst and such was determined or suspected.
NOR, if she were seriously injured, could he run any risk of her being hospitalized or subjected to serious medical care where the evidence of such molestation (vaginal discharge & distention, breast buds, others)...would become known.
There are too many circumstances under which he would have had to kill her, esp if she were about to tell her teachers or run away from home.
The VDs may also have been pimping her out for money, that would explain the constant sexual activity on the part of a 7-yr-old.
This seems the most important point made so far.
The condition of her body when found makes it seem like SOMEBODY had intentionally made sure no evidence of how she died or if she had been sexually violated was found.
NOW, any pervert, random killer, wouldn't give a darn. WOuldn't go to that trouble.
Pretty much leaves ONLY ONE ANSWER.