@b4343,
I think marrying the same person a second time is pretty unusual, in and of itself.
And ultimately it's about whatever works for you guys.
That said, I can see why she'd want a new ring in terms of the symbolism (which is what the ring is all about after all). The old ring accompanied a lot of vows that turned out to not be kept. ("For better or for worse," etc.) The old ring is connected to an old marriage, that did not work out.
A new ring for a new marriage -- hopefully one that will last longer and work better -- makes some sense.
I don't know about the "dream ring" stuff but that would seem to be its own issue. If you happened to meet her 3 years ago for the first time and were getting married now, would you want to get her a "dream" ring?
From re-reading your post, you say that the "dream" ring was fine with you until someone else expressed surprise. If it's fine with you and it's what she wants, go for it IMO.