I'm a little fed up with customers not reading listings, I got an order for a sewing pattern on my other shop, a fact which was clearly stated in the title, description, it was 5.00 and there was a big 'instant download' banner across the picture, but they sent me a rude email a week later asking where the plush was. I noticed the very day they purchased it that they'd downloaded the file immediately, too. Baffling! I explained it to her very patiently and politely, and said that as she'd downloaded it I couldn't give her a refund.
I wasn't left feedback (at least as far as I am aware) but if I was, I'd have responded to it publicly, stating quite simply that the buyer hadn't read the description, though it was clearly marked as a sewing pattern, not a plush - or, in your case, a single ornament. If she doesn't want to work it out then that's all you can do. It's just for the sake of other customers so they know what happened.
Just be sure, IF you do decide to reply publicly to the comment that you keep your cool, remain polite, professional and informative and don't lay any hostile blame on the customer. Sometimes they just miss things.