Sorry to hear that, but I'm not sure there's anything more you can do until you have some more information about the package itself, either if it shows up in Canada and you can appeal eBay's decision, or if Aus Post can't find it and you can claim some compensation.
Obviously your buyer will be uncooperative, but otherwise I would have suggested asking them whether they could submit an enquiry with Canada Post with the registered number and see if that gets any faster results.
To be honest, buyers who have behaved like yours has actually make me a little suspicious. Most people who have been waiting a few weeks for an international package don't suddenly think "scammer" and ignore valid proof of postage. 
Received last night at 12.05am
Hi vintageandantiquejewellerystore,
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Thanks for your message. The case you contacted us about was closed after we made a final decision on it. We'll review your question or concern and get back to you within 48 hours.
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You can view the details of this case in the Resolution Centre.
Received at 12.10am
Thank you for contacting eBay in regard to the Charm Bracelet, eBay item# ************, you recently sold. My name is Lesley and I am a specialist for eBay's Resolution Center. I know you are concerned about the result of the case closure. I want to make sure you understand why the claim was closed. Let me explain our process and help you get this resolved.
Unfortunately, at the time eBay had to step in and make a decision on this case, we could not verify that the item had been delivered. The tracking information provided (************) is invalid and cannot be traced online. If a buyer has not received their item and we do not have proof of delivery, then a full refund is due to the buyer. Please understand that if the buyer says the item was never delivered, tracking information is the only way we can prove otherwise.
We cannot grant an appeal on this decision because now that the refund has been issued, we're not able to take the funds back from the buyer. When eBay makes a decision on a case, we can only use the information available at that time; the original decision was correct based on that information, so the case is not eligible for an appeal.
So there is not right of appeal. Since when or has she simply for once told the truth. Dont both appealing as we have already paid the buyer.
and yet Ebay policies state
Appeals
Buyers and sellers have an opportunity to appeal our decision within 30 days from the day a case is closed by providing appropriate documentation in My eBay.
and
We reserve the right to correct any processing errors we discover by debiting or crediting the payment method used for the incorrect refund or reimbursement.
