Your seven day Returns is trumped by eBay and Paypal's policies.
EBay allows Disputes for 30 days after delivery and PP allows Disputes for 180 days after payment.
Now.
Either the buyer returns the item (eventually) or not.
If she returns it, you refund.
If she does not return it, you don't refund.
Whatever you do, try not to let it go to a Dispute.
EBay can demand that you send the buyer a Return Shipping Label. If she is not in Canada, this is impossible. You will have to negotiate with the unhappy buyer whether she pays for the return and you refund her or whether you send her money for the return and hope she doesn't just keep it and the dress (giving up the refund).
This, BTW, is based on the reason your buyer chooses for her Dispute.
If she wants to return it and get a refund, don't argue.
It business, not personal. And you get hurt more than the buyer.