Yes, I´ve read a bit on the "Por Bem brooch", I also was unnaware of its existence. I really must dig into that book!! As far as I know there are no pictures of any of the ladies wearing it (not that I have seen, that is). I never saw any pic of Dona Isabel wearing it and she has it since her wedding. As you say it has a truly fascinating story, and it really makes me wonder what jewels we don't know about stay in the royal vaults for decades without being worn. I assume the pictures on the book are copyrighted and we cannot post them here? Most portuguese books have a paragraph stately forbiding any kind of copy from its contentes and it is also forbiden under the portuguese law.
As to Dona Isabel's title...I am no expert in titles but I assume her "HRH" styling doesn't come from the fact that she was born as Miss Isabel of Herédia . She gave up her maiden name when she wed the Duke of Bragança and became HRH Dona Isabel of Bragança (according to the web site of the portuguese royal house the correct title would be SAR a Duquesa de Bragança, Senhora Dona Isabel). We often read in the press things like "Princess Letizia Ortiz" or "Princess Mary Donaldson" (again elevating the Ortiz and Donaldson families to princely rank), but I think the new director of the Ajuda Palace should be aware of these styling details .
On a final, and funny, note, many years ago I read an enterview with the Duke of Bragança where he was asked about his wife's popularity after they married. With his usual sense of humor he said she become so popular that people started adressing him as Dom Duarte of Herédia!