Kathy,
I don't have any knowledge for you about bargaining tactics in Istanbul -- although others who have been to the bazaar will undoubtedly have good advice -- but I applaud your caring attitude. I like to get a good deal as well as the next person, but it is so important to remember that sometimes a small amount extra, such as maybe in a tip, would mean so much more to another person. An added unfortunate aspect of your story is that the woman's behavior bothered you much more than it ever did her, I'm sure. She doesn't sound like the kind of person who would lay awake at night wondering whether she had treated someone fairly.