My observation is that no royal woman other than the Queen wears different tiaras from the royal collection. A royal woman may switch tiaras but once that switch happens she wears that tiara until the next switch. For example, Catherine wore the Halo Scroll on her wedding day, then she switched to the Lotus tiara and now she wears the Lover's Knot Tiara. I don't think that we will be seeing her in the Halo Scroll or Lotus tiaras again, and if she debuts another royal collection tiara, which I doubt, then we will not see her in the Lover's Knot tiara, at least not during Queen Elizabeth's reign.
Same thing with Camilla, she only wore the Delhi Durbar tiara once and then she started wearing the Greville tiara, there may have been another tiara in between that but there are no photos of her in that tiara, but she has not been seen in the Delhi Durbar after she started wearing the Greville.
With Sophie, I am pretty sure that she has not been spotted in her wedding tiara after she debuted the aquamarine tiara in 2012.
Camilla and Sophie wear other tiaras like Sophie's other aquamarine tiara, the one that doubles as a necklace, but those seem to be private acquisitions or family tiaras. The more I think about it I suspect that Sophie's aquamarine tiara / necklace combo was probably gifted/funded by the Queen and will be the Wessex family tiara.
What that means for Harry's future wife is that, if he gets married during his grandmother's reign, his wife will be given access to one tiara from the royal collection, but switching will be allowed, and she will also be gifted a tiara. Now all of this can get turned on its head when Charles becomes King.
