I wouldn't tell her anything about my health or any other subject I was uncomfortable talking to her about. If she brought it up, I'd have a pat sentence like, "I don't wish to discuss that. . . now" or, "with you," however you can word it so it closes the door on discussion without upsetting you unduly. Maybe, "at this time"? Before you go to see her, make a list of things you can, would like to talk about in detail so you'll always have something to change the subject to.