I don't think there was a need to state there was no authenticity card. If there had been one originally and it was lost, that would be one thing, but if H doesn't even have them, then I see no reason to mention all the things that aren't included.
Did you mention in the copy that it was a petite or small size? Sometimes people just have no conception of size, even when measurements are given. You may have done this already, but if something is really small, to cover yourself, it's a good idea to say that it is petite, tiny, etc.
However, it is up to the buyer to understand what she is buying and I see no reason to let her return it. I, like you, would be afraid it was a fake one being returned or that it was dirty, etc.
I hope everything works out OK. I hate hassles like this, too!!