She did have another diamond and pearl tiara, maybe the painting shows her with that tiara in another version (2nd frame?).
--Previous Message-- : The striking thing to me is the apparent lack : of symmetry in the diamond elements. The : pearls are also different from each other in : shape, size, and color. I wonder whether : this headpiece was a combination of old : pieces. It does not have the regularity and : design coherence of the GGBI tiara. But it : is a very interesting jewel. :