I am an American (norteamericana) married to an Argentino and I am commonly called gringa. At first I was offended, but it was carefully and repeatedly explained to me that this is just a descriptive word for a foreigner from Europe or North America and not intended as an insult. After all, the Argentinos call each other Gordo, Flaco, Viejo, Negro, etc. In the family, I am affectionately La Tia Gringa, but it is not just family. On our block in Balvanera, when I am not around the local merchants routinely ask my husband "Donde esta la gringa?"
I don't think the Argentine terms "gordo" etc are at all nice. It's an insensitive aspect of the culture that needs change. I don't believe that any overweight person wants to be called "fatso" or a dark skinned person "Black" etc. Calling someone "gringo" or "yanqui" is similar to a Spaniard calling an Argentine "Sudaca". People have names and should be addressed correctly not by a physical or racial trait or a sarcastic term.