This is an odd situation -- the TA's, not Argentina's (although that one is also odd).

Wire transfers from US to Argentine bank accounts usually involve high commissions, so while I understand her needs, a wire transfer doesn't seem the right option. Unless, of course, she is asking you to do a wire transfer to a US bank account, in which case:
1) you need to really trust her;
2) you should start some heavy bargaining, as there's no way the Argentine tax authority will know about wire transfers between the US accounts, i.e. she will skip paying taxes over her services.

I would never do a wire transfer to a TA (neither in Argentina nor anywhere else) for obvious reasons, and I also believe there are no services TAs offer that I cannot book online. But if you really want to use her services, I would offer her an advance payment through credit card and the rest you pay upfront in crispy green Franklins once you get to Argentina. If she is so worried about the volatility of the exchange rate, this should fit her needs.