Hi OP,

I would disregard the claim, or reply with saying the items are genuine, go and ask Chanel counter in a dept. store.

Why even give her any money?  Tell your buyer no refund, and if she even thinks of slandering you in a f/back claiming the items are fake without an irrevocable proof you'll report her straight to Chanel - let them deal with her for degrading publicly their products.

And paddy, OP doesn't have to prove anything, buyer would need a proof to back up her counterfeit claims.

Also, maybe you can't send counterfit stuff through the post, but who's to deem them as such? Post Office staff? Not only that, they would need to open the satchel and have a look and then somehow decide they are indeed counterfeit - as if.

Buyer got them just fine through the post to start with - and you are telling OP that she can't have them back the same way (not that she wants them back - why should she, she sold them, got paid, buyer got her items - end of story)