Well, the ring is unique as an engagement ring, but the overall style and size don't convey "special" to me. Not that it has to cost an arm and a leg to feel special, but this looks too much like trendy jewelry that younger women wear, that doesn't necessarily have the ability to 'mature' with the woman. There is a tremendous amount of beautiful, special, and unique options somewhere between a diamond in a pink halo setting and this amber heart.
I personally think it is odd nowadays that some of these traditions still exist, like a man picking out a ring without the woman. It sounds like earlier generations, where a man proposes and a woman accepts, rather than them jointly embarking on a future together and making decisions together. If you want to honor the tradition of wearing a ring, can't you pick it out together?
She should gently let him know that this isn't her taste. It won't be the first time in their life together that they just didn't see eye-to-eye on something and they need to communicate their way through it.
Personally, I wish I had gone with something more unique. And these days I'm inclined to make a more socially-conscious choice rather than a mined diamond. I'm considering a slight change (still very traditional) to my ring-- I'd love a canary yellow lab-created diamond.