This Emerald set of jewelry is very beautiful such a shame D. Isabel doesn't make use of these jewels. I also though it could be possible that these jewels were inherited by D. Duarte's 2 brothers and that's why D. Isabel doesn't wear them, but knowing that she has others jewels she rarely or never wears it could just be she doesn't like large ostentatious jewelry.
Here we see a picture taken during Duarte Nuno and Maria Franciscas engagement and she wears the earrings. So in my opinion the earrings (and possibly the brooch) weren't wedding presents. Could they possibly be engagement presents? Or maybe early wedding presents from her parents? Who knows maybe we'll write to Dom Duarte and he'll answer us lol
Here are 3 more pictures of Dona Maria Francisca with the earrings and brooch.