Lotta diamonds, and they are the brightest part of the image as they should be, but the picture is really too soft to see them. I would cut the diffusion filter. If you want a softer look, do it with softer light or try using more shadow for a low key look or even a grainier film. If the necklace is the subject, you want it to be visible in detail.
The hair looks a little flat, so maybe a more specular light in front up top, but that might not be necessary if you remove the diffusion.
I would also arrange the necklace and the model so that the pendant hangs straight down.