I would not do too much. The Spanish monarchy is not like the Scandinavian ones with so many gala events. The events for which grand jewels are needed are quite limited.
As Letizia is just a very petite lady, the major Spanish diadems overwhelm her and in combination with her frêle appearance make her looking like a beauty pageant Miss. So my advice would be: at least bring all jewels to the jeweller for a profound cleaning (= remove every stone out of the setting, give every part an ultrasone cleaning, repair or improve the montures, re-silver the settings and bring it back to a fantastic sparkling state), ready for the future, ready for Doña Leonor and Doña Sofía.
Letizia in the meantime: make use of the (cleaned) Floral Wreath Diadem or the (cleaned) Prussian Diadem. The other items are best left in the cassette. She simply misses the statuesque presence needed to wear the big and outspoken diadems. My personal opinion. And, oh yes: that Ansorena-shaming insult to craftmanship, the "modern" fleur-de-lys diadem, is best thrown in the shredder.
