The Queen is up in her 90s or so. I would think her trendy staff drafted this trendy proclamation for her. They were pro-active and The Queen just signed on to it. Which she should not have. It seems to me that Royal staff tilt gay anyway and always have everywhere. So they influenced her.
No, her staff didn’t draft it for her. The government of the United Kingdom did, in consultation with the governments of the Commonwealth Realms, and if requested, it is part of her role to sign such a document if requested by her Prime Minister and to make such a speech if Her Majesty’s Government requests it. Unless it is unconstitutional, she does not have a choice.
That’s her role within the Constitutional Monarchy - to give the Royal Assent to the acts of Her Government except in the most exceptional circumstances of Constitutional violations. She is not an absolute Monarch with the power to overrule the wishes of the elected government of the United Kingdom, or any of the Commonwealth Realms. She has the right to be consulted, to encourage, and to warn, in private conversation with her Ministers (most generally with the Prime Minister) but she must act on his advice unless his advice or the actions of the government are outside the scope of constitutional law.