Paypal dispute problem

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I recently sold an item but the person that bought it says she hasn't received it yet, its only been 4 days since its been sent and I already told her it will take a little over a week for her to receive. She keeps on threatening me she will open a dispute but I keep telling her to wait. Also my policy is if the item gets lost or stolen in airmail it is not my problem. Also its not a Ebay problem. If she files a dispute what should I tell the paypal people, is it more likely for her to win or me?