Dont even waste your time on this one. Tell her to take it up with paypal if she thinks they are fake.

This reeks like a scam to me anyway, demanding you send her $ back right now? No, thats not how it works. You get the item back and then send the refund.
Which I Totally do not recommend you do since she needs to prove that the item is fake - its on her. And she cant do that since they are REAL.

Let her know shes going on my blocked bidder list and Im sharing her ebay name with other major powersellers who sell auth jeans.