Before filing SNAD, verify that it's fake by posting on the appropriate "authenticate this" thread here, on the ebay community fashion board or you can pay for a professional authentication. (I don't think a purchase/professional is necessary unless you're unable to confirm inauthenticity free.)
Once you've confirmed that it's fake, open a SNAD case. Generally, it's recommended that you try to work it out with the seller prior to opening a dispute but since the seller already told you that she'd want you to pay shipping in both directions, I recommend you go directly to the SNAD route.
With SNAD, the seller has to pay for return shipping if she wants it back and once received, you're to get a full refund (including your original shipping) so you're made whole.
If the seller doesn't respond to the dispute within the timeframe ebay requires, you can escalate it and ebay will resolve it. You'll win the dispute and get a refund, either after returning it with a prepaid shipping label paid for by the seller or without sending back the fake.
A request about a Mulberry bag was posted on Monday. The authenticator responded with a request for more pictures but no further response. not saying it is the same bag, but..........
