Your wife should stay away from mainstream grocery stores and seek out olive oil and vinegar stores. The good California EVOO brands are authentic and win international awards. You can find them in good grocery stores.
There's a really good olive oil and vinegar store in Burlingame, CA called Del Oliva. The owner is an encyclopedia of olive oil facts. He talks about why his oils are good (harvest time, which country, which time of year, how fast the harvest takes place, type of pressing, blends) and he suggests that lots of commercial EVOO is doctored or fake. I like buying his oils and vinegars.
There's an incredible olive oil store in downtown Missoula, MT called Tosca Olive Oils. I've seen lots of good oil collections, but this one is up there with the best in terms of variety. I haven't bought from them, so don't know about the quality. But the size is impressive.
