Although she was Commander-In-Chief, she gave responsibility to the prime minister and the Secretary of State for Defence, along with other officials. Theoretically she could have ordered a strike against the white house but this would be vetoed by the govt.
She had the ability to declar war, however the government doesn’t need the Queen’s permission.
She could have issued an order of Dissolution of Parliament, but parliament is not the same as the government. The British government is the one that actually rules in the UK. Also such an act would have caused an absolute uproar among UK citizens and probably ensured the beginning of a Republic
So she has "power" in name only, but no real power which was my point, everything has been taken away from her ... and now also King Charles.