Ebay and paypal rules, state that you must send an item by trackable means or you are not covered. Therefore the sender is not covered and must return your money to you if she cannot locate the dvd in the post system. Go to the dispute centre and enter it in as a dispute saying that you have heard nothing from the seller despite having contacted her. They will then approach the seller on your behalf and if you paid by paypal they will automatically deduct it from her paypal account and send it you you. They may also block the seller from ebay for a while.