This spider was on an exposed ridge overlooking the sanctuary. She appears to have caught a nice sized wasp.
This species often creates an X-shaped design (stabilimentum) in their web, and you can just see a hint of one extending to the lower right.
The common name Silver Argiope is consistent with the scientific name (argentata = silvery). Even the common name in Portuguese, Aranha-de-prata, translates as Silver Spider. It is indeed silvery.