While you can decline to accept returns, if you take Paypal you make refunds.
So you may as well be gracious.
The buyer is being very polite and pleasant about an unusable (to her) item.
When the item turns up, let the customer know, thank her for her prompt return and good packaging, refund her original payment and relist the item.
You can also at that time ask the buyer to agree to a Mutual Cancellation,which will get your fees back, if she agrees or ignores the request.
Not every transaction will be smooth. It's business not personal.
I use the 14 day returns too, but mostly because
a) eBay gives sellers who do allow returns a fractionally higher placement in Search
b) refusing returns turns off good but nervous buyers
c) it marginally discourages scatty buyers who are not sure whether they are happy or not.
d) most of my products are used. They're not going to get less used by being returned.
Never goes smooth, how come it never goes smooth-- Captain Malcolm Reynolds