"The fact that she insists on wearing an item that she is proud to have purchased on her own in a symbol that represents the two of them is rather telling. And I think it's telling him that what he offers her is not, in her estimation, good enough."

Traditionally, men buy the engagement rings. It's a ONE half of a couple purchasing a symbol that represents the WHOLE. Frankly, I don't think you can buy a symbol...something becomes a symbol through the way it's used and the meaning you begin to associate with it. What we have here is one item that has two symbols to two different people. She sees it as a beautiful, expensive piece of jewelry that she picked out herself. She loves the diamonds and is perfectly willing to reset them, so they can have their "own" ring. Her ex-husband, since she purchased the stone herself, is nowhere in this symbol. HE sees it as the symbol of a failed marriage, and maybe has a bit of insecurity about his ability to provide a better stone for her. She's being, in my non-superstitious opinion, prudent and practical. He is being a sentimental twit. If the diamonds are a sticking point, why not forgo the rings entirely? Lots of people (like my parents) get by without this symbol.