I doubt if the writers of the sites PaulP gave links to have even read the news reports much less looked at the actual will.
When I initially posted the news items, I was challenged by the experts for whom knowledge is immutable. As a result, I looked at the will.
Queen Mary was definitely left the 2 diamond rivieres. Princess Alice, Countess of Athlone got the diamond brooch.
That is all the jewellery given to the royal ladies.
Queen Mary was left other items, and it maybe that today some of those items are in the Royal Collection. I have never cross checked.
But nothing was left directly to the Royal Collection.
Lady Mount Stephen directed that her pearl and diamond tiara was to be sold and the proceeds given to the King Edward Hospital Fund. That is what occurred. Did she have more than one tiara? I don't know. If she did, it would have been inherited by her sister.
Apart from named items of jewellery given to named ladies, the residue of the collection went to Lady Mount Stephen's sister. The jewellery collection is not itemised in the will.
The other items inherited by Queen Mary included enamel portraits of various earlier Kings and Queens, tortoiseshell boxes, 2 items of French Marqueterie and portraits by Allan Ramsay of George III and Queen Charlotte. These, it was noted, were formerly in Gloucester House.
Both of these are in the Royal Collection.
Queen Charlotte https://www.rct.uk/collection/402413/queen-charlotte-1744-1818
George III https://www.rct.uk/collection/402412/george-iii