My stock "answer" to what I consider nosy questions is to smile and then either turn my attention to someone else or walk away. I used to belong to a social group where there was one woman who would ask really nosy intrusive questions (including asking about how I could afford xyz, so along similar lines as what you're dealing with). I never ever replied verbally. I just smiled and then started talking to someone else.
Now, the alternative to that is to actually confront her with the very thing she is supposedly criticizing you for.
Hyacinth: Is that bag from X designer?
Me: Yes. I paid $500 for it! Isn't that great?
Hyacinth: That's a complete waste of money. I'd never want to waste that much money on a bag.
Me: Too bad. I would. And did. And I'm pretty darn happy with it.
In other words, gloat. Now, normally, obviously, it's not something you would want to do. But heck, she's asking for it so I see nothing wrong with throwing it right back in her face.
And no. Absolutely Positively No Way should you stop wearing these items to the office. I'd purposely wear them and keep flaunting it. You could even make it a point to stop by her desk and let her know just how much you did pay (and pad the number if you want). Sort of head her off at the pass. I'll bet that will shut her up in short order.
There's really nothing to be ashamed of. You earn your money and it's your perogative to spend it any way you see fit. She's making you feel bad for something you shouldn't be feeling bad for. By making her realize you don't feel bad at all, and in fact are proud of how much you spent, you will completely deflate her balloon.