Yes, I can see why she is upset. Like others said, there is nothing wrong persay with this question if it's in the right context.
Exactly what is Asian food anyway? Chinese is very different from Japenese which is very different from Thai which is very different from Korean. It's like saying "Hey, all Asians are the same, and even though you were born and raised in Anmerica you shopuld still be an expert on all things Asian. So where should I eat?" Honestly, no one ever asksmewhere the best German restaraunts are!