President Biden orders flags at half staff after the passing of HRH

[Celerity]

26. it is literally in the title of the OP (and it is wrong anyway, she was addressed as Her Majesty,

not Her Royal Highness.)

https://en.wikipedia.org/wiki/Royal_Highness#United_Kingdom

In British constitutional law, use of the style HRH or simply "Royal Highness" may only be conferred by letters patent and only to children of the monarch's son. It is typically associated with the rank of prince or princess (although this has not always applied, an exception being Prince Philip, Duke of Edinburgh, who received the style in 1947 prior to his marriage to Princess Elizabeth but was not formally created a British prince until 1957). When a prince has another title such as Duke (or a princess the title of Duchess), they may be called HRH The Duke of ....

For instance HRH The Duke of Connaught was a prince and a member of the royal family, while a non-royal duke such as The Duke of Devonshire is not a member of the royal family, but is a member of the peerage. When Edward VIII abdicated the throne in 1936 he was granted the style and title, HRH The Duke of Windsor. The woman he then married became the Duchess of Windsor, but she was denied the style HRH. Edward for much of the rest of his life attempted unsuccessfully to persuade the crown to grant her the style.

According to letters patent issued by King George V in 1917, the sons and daughters of sovereigns and the male-line grandchildren of sovereigns are entitled to the style. It is for this reason that the daughters of the Duke of York, Princess Beatrice and Princess Eugenie, carry the HRH status, but the children of Anne, Princess Royal, Peter Phillips and Zara Tindall, do not. The children of the Prince Edward, Earl of Wessex, at the request of the Earl and Countess of Wessex, are styled as the children of an earl, and thus are known as Lady Louise Mountbatten-Windsor and Viscount Severn.

Under his letters patent, only the eldest son of the eldest living son of the Prince of Wales was also entitled to the style, but not younger sons or daughters of the eldest living son of the Prince of Wales. Queen Elizabeth II changed this in 2012 prior to the birth of Prince George of Cambridge so that all children of the eldest living son of the Prince of Wales would bear the style, returning to the position Queen Victoria had instituted in 1898.

There is no mention of younger living sons of a Prince of Wales, as a result of which the children of Prince Harry, Duke of Sussex, Archie and Lilibet, are not automatically a prince and princess with the HRH prefix. On 18 January 2020, Queen Elizabeth II announced that the Duke and Duchess of Sussex would no longer use the style of His/Her Royal Highness due to their decision to step down as working members of the royal family, though they are still legally entitled to the style. On 13 January 2022, it was announced that Prince Andrew, Duke of York was no longer afforded the style, following a notorious lawsuit against him.

Letters patent dated 21 August 1996 stated that the wife of a member of the royal family loses the right to the style of HRH in the event of their divorce. Examples include HRH The Princess of Wales and HRH The Duchess of York whose styles changed to become Diana, Princess of Wales and Sarah, Duchess of York, respectively. These styles are in line with those of a divorced peeress.