I got her DNI and her CUIT. This information is public, so I don't think I'd be violating any rules by posting it.
If you go to this website:
http://www.nic.ar/entidades.html , and type in her name, it brings up her DNI and CUIT, which I suppose are associated with her domains.
The DNI is the same number provided by Globinfo.com.ar (not sure how official they are, though).
I guess the next thing to do would be to buy a copy of her Veraz, and that would be the ultimate proof. Wouldn't the Veraz show whether she was allowed to rent the apartment or not? Or do we need to go to another database for this?