Great pictures Ella, as always. I agree, it is a shame that we don't have more images of Ella in formal dress with her jewels.
These emeralds must have been quite something in the flesh. If you look at the photos of Mignon wearing them, you can see quite clearly how large they were. I think that the necklace that she is wearing was remodelled for her (by Cartier?) from Ella's original necklace; nevertheless it is quite some piece of jewellery. As a point of interest, her mother bought Miechen's sapphire and diamond tiara (which Pcss Ileana inherited) and a huge sapphire from the exiled Ferdinand of Bulgaria, which was suspended from the end of a wonderful diamond sautoir.
The only photo that I have ever seen of Maria Pavlovna in anything like formal dress is the photo taken at her wedding; her tiny figure looks swamped by her dress and jewels, some of which may be Ella's.