The duchess has said she was given a choice:

https://www.dailymail.co.uk/femail/article-6319905/Meghan-Markle-recalls-surreal-day-Queen-helped-pick-wedding-tiara-Buckingham-Palace.html

So what do we think were the other choices?

I must admit I'm a bit stumped. I'd have though the fact that the DoC wore the scroll would have knocked that out of the selection.

So maybe the palmyrete (please someone give me the right spelling) or the Empress Marie sapphire bandeau or both.