Her Majesty can stop this nonsense anytime she wants to. That’s the point of a constitutional monarchy. She is no mere figurehead as a recent PM discovered when an admiral stated that his oath is to the Queen.
If she stood up against Marxism the military and the people would stand with her.
I remember reading a biography of the Queen many years ago, and it contained a discussion about the benefit of having a constant leadership entity that was apart from and above politics and that unified the Nation.
I don’t remember the author, or where the quote came from (Churchill?) but the idea was that when things go bad politically in the UK, the people vote down the Prime Minister - but still sing ‘God Save the Queen’.
(I”m not saying it would be right for us, here - but it has always seemed to work for the UK.)
The Queen can only act to stop a government that is acting unconstitutionally.
Unfortunately most of what British governments have done to damage the UK is perfectly constitutional.