Open an account in your girls name, and never do digital delivery for any over $100. Just put on CD, and ship it to their paypal address, then give them the download if you wish, so if this happens again you can give paypal the tracking I.D Paypal always ask you for shipping tracking code, because this is what they want all sellers to do so they can side with them... This is why ebay requires download to be shipped on cd's now. They know people are professional refunders, so they ask merchants to do their part and ship what ever it is on CD or DVD. When I was a noob years ago, I refunded a fake dispute because I was always aware of how people scam online and didn't have a problem refunding, but I called a paypal rep just to see how I can avoid this kind of stuff, and she told me no matter what you sell, even if it's virtual, always send it on a cd. Paypal uses a 3rd party to resolve disputes, and those parties are mail shippers like USPS, UPS, Fedex ETC...
maybe, you can create an another account in another person id. so you cannot use your own id, if you remove your negative balance