The seller finally contacted me today. She said that she thinks her account was hacked. Sounds like it was both eBay and Paypal that were hacked, maybe? She said she just got my message and she was very sorry and that her Paypal account had been frozen for 21 days. I'm unsure about her eBay account and that she hadn't opened the chargeback. I'm assuming she had some kind of fraud alert on her account and it was automatically opened on all her transactions. Unfortunately, when I had called Paypal they said there was nothing unusual going on with her account. But it seems that's the only thing the seller and I can figure out is that the fraud alert is what caused it to open up the chargeback.
Anyhow, I've asked her to send me a request to amend her feedback. I'm still scratching my head over the whole thing, but at least I've finally heard back from the seller.