You are correct that as a private seller you don't have to refund for buyer remorse returns. EBay even uses the example of clothes that don't fit to explain this.
That's the theory! The dilemma for sellers is that buyers can easily "discover" (or even create!) some damage or fault in the item. They can then open a money back guarantee case, when the seller has to refund them in full, and send them a prepaid label to return it. EBay will automatically find in the buyer's favour, without requiring any evidence.
As usual on eBay, it's easy for buyers to run rings around the the rules designed to protect sellers.
If this doesn't happen but she leaves you negative feedback, look carefully at what it says. Buyers are not allowed to leave negs because a seller refused to do something that eBay doesn't require them to do. You're not required to accept buyer remorse returns, so if she gives this reason for a neg you may be able to get eBay to remove it.
