Many thanks Bryce for sharing your thoughts. IIRC, at appearances during her four day stay in Nigeria in 2003 we saw around three brooches, and three demi-parures (pearl & diamond, sapphire & diamond, and all diamonds) that were new to us. It would be very surprising' but certainly not impossible that some were loans.
In link below to The Court Jeweller article, notice the earrings from the pearl & diamond suite worn by QEII for 5 December 2003 CHOGM dinner being worn by the Princess of Wales at last year's Trooping the Colour. Hoping that other pieces (especially the diamond earrings) from that tour will reemerge.

https://www.thecourtjeweller.com/2023/11/the-princess-of-wales-honors-the-late-queens-memory-with-pearls-on-remembrance-sunday.html