Hmmm no... it is too much a fence. It was already unwearable for Queen Wilhelmina (she only wore it for photo shoots).
Imagine Princess Máxima in a simple white gown, no sash, nothing. Posing in the white dining room at Huis ten Bosch Palace. No diadem. This stunning collier, the matching bracelets and two simple diamond-and-sapphire earknobs. No less, no more.
G-l-a-m-o-u-r !
The book by René Brus (Juwelen van het Huis Oranje-Nassau) only mentioned the diadem broken up to make personal bijoux for the four daughters of Queen Juliana. There was no mention of the collier being broken up as well. And as John said: the elements on the "diadem" worn by Princess Máxima come from the collier, that seems to indicate it is still around.