I have never sent an ATM card, only a VISA gift card and I used DHL which seems to have a much larger presence there than FedEx. But either one should be safe enough to get it to her. Under no circumstances use the post office, not because of ours but the Argentine post office is pretty unreliable.

I am sure there is a way to do an international wire transfer you would just need to check with your bank on what routing and account information they would require. The national bank used to take a conversion fee for wire transfers, not sure that is still the case or not.

The most common method to transfer money into Argentina would be Western Union. They charge a pretty hefty fee but the money is almost instantly available for pickup.

Sam