Regarding the term Queen Mother, both Queen Alexandra and Queen Mary were referred to as Queen Mother in the early years of widowhood.
Edit: and I'd say amethysts. Edit 2: compare the colour of the jewels with the colour of the sash.
Edit 3: There are two requirements for a Queen Mother - first she is a queen and, second, she is the mother of the monarch. Thus, for instance, Camilla could never become Queen Mother. Edit 4: Queen Adelaide was not Queen Mother. She was a queen but not the mother of Victoria.