There's a chargeback fee (that paypal takes) if the seller loses the chargeback. I thought it was $25 but that was years ago.
Does it say what the reason is for the chargeback? For other than SNAD, your seller protection should kick in.
But since you say the buyer claimed snad (on ebay), you are obligated to accept the return and either pay for ebay to provide a return shipping label or you can supply your own prepaid label and send it to the buyer through the dispute.
THen the buyer has a certain number of days to ship it back to you.
If you don't respond to the dispute in time, the buyer can escalate and ebay will resolve in the buyer's favor and your account gets dings.
If you did respond and provided return shipping but if the buyer didn't return it, you would win the dispute but you'd have to call ebay to have them close the case.
ETA: What is the timeline for this transaction? By what date did you have to respond to her SNAD claim? How did you respond to the case? Through the case?