The worse buyer I have ever met

If she says it's fake and files a SNAD, she's going to have to get documentation and pictures to back it up. That being said, paypal will take virtually any kind of documentation. So yes, send a copy of your receipts to paypal and hopefully you have saved the pictures of the item to provide to paypal as well. I'm sorry this happened to you. I hope it works out in your favor.

Paypal does not only care if the buyer received the item or not, but if they file an item not received and the seller provides proof of delivery, then the claim will probably be found in favor of the seller. However, if the buyer files an item significantly not as described, then things get kinda tricky, especially if the buyer paid by credit card.
 
Be very careful about bait & switch here. Buyers buy an authentic bag then return a fake one. Paypal will refund their money because you have received a bag back from them they won't care if you received the original bag or not!