You mean the address you gave in your Paypal account has a Cambodian address?
If the seller shipped anywhere else, including to a Canadian eBay address that was not also in your PP account, she lost her Seller Protection.
So first, has the item been paid for?
Has it been sent?
How much postage were you charged? (The amounts would be different for Canada and for Cambodia).
If it has not been sent, go to your PP account and make sure you have your correct (Canadian) address there.
The seller can safely ship to that address.
Now you can correct the eBay (Cambodian) address at your leisure.
If the seller has sent the item, it cannot be delivered, since I assume that the only part of the address that is wrong is the country.
If it gets to Cambodia, eventually it will be returned to the seller.
It's hard on the seller, but since the item will not be delivered, if she is obdurate about not refunding (and this is NOT her fault, it is YOUR responsibility), you could file an Item Not Received claim. But again you caused the problem, not her.