After a lot of checking I have not found the source for the belief that Sophie’s tiara, worn by the Queen in 1970, was ever connected with the source of gems for the remake of the Queen’s aquamarine tiara. No connection whatsoever.
Except that the “belief” that it was is all over the internet, including Ursula’s page which does not provide a source, same as others don’t.
Have checked Young, Menkes, Field, Bury, Munn, and online Royal Collection, and done a lot of googling.
I feel that the fan/shell elements in the Queen’s aquamarine tiara were lifted holus bolus from somewhere - presumably from the V-shaped hair ornament gift of 1968.