I think you've gone the polite route. She doesn't seem interested in curtailing her behavior. So in this case, I believe it's time to light it up in proverbial neon for her in terms that even she can understand:
"Your incessant personal questions are inappropriate. My affairs and those of my family, are none of your concern. Nor do I wish to hear comment from you about any of it. You would do well to just keep tabs on the inner workings of your 'own' life, and you'll have plenty enough to do. If you can't control yourself and won't respect my boundaries on this, then our rel@tionship is finished."
And MEAN it! If she insists, then cut her off completely. There is no reason to allow someone like that to bully their way into your personal life.
ETA: And on the flip side, make sure you are not sharing anything with her that she will feel free to comment about, or hold over you later on. In effect, give her NOTHING to say. And if she says it anyway, she's no longer welcome in your world.