When I got engaged, I had people have the nerve to ask me "Oh, how many carats is it?" or "How much did it cost?" Luckily, with an engagement ring, you can plausibly say that you don't know. I would say, "Oh, I'm not sure, Fiance didn't tell me. But I just love it, blah blah blah!"
With this woman, I would just be direct because it sounds so persistent and annoying. "You know, Sally, I have to say that I find it super weird and really intrusive that you always ask about my belongings, their cost and origin. Those things are none of your business, and I don't believe your opinion of my purchases is any of my business. So, in the future, when you ask me questions like that, I'm just not going to answer them. I'm just letting you know now so if I don't respond to you in the future, you know why."