I don't think it's that exceptional for a 6yo. I certainly see no reason to suggest that the OP is lying, and although the child is clearly bright, she wouldn't need to be a genius to come up with something like this.
My dd would certainly have known all of the words used at 6, with the probable exception of foot soldiers, and her spelling was generally very accurate by that age. Her punctuation was less reliable, and I doubt she'd have used the comma, but she was very secure with full stops, capital letters and exclamation marks at that age. Now, at 8, her writing is much, much more sophisticated, so when I read the OP, I assumed that the child was probably around 6ish.
Some kids just have a natural flair for writing. They may read a lot, and enjoy playing with words. I think it's a bit
to suggest that the OP is lying. I can easily believe that a bright 6yo wrote this.
It's a lovely piece of work, OP, but I wouldn't worry about the levels at this stage - just nurture your child's love of words! :)