Walter Bagehot in his classic study of the British constitution wrote what is now accepted as the definitive statement of the rights of the monarchy. Those rights are 'to be consulted, to encourage, and to warn'. No more than that, and no less. Bear with me if I quote what Bagehot said at slightly greater length:
"To state the matter shortly, the sovereign has, under a constitutional monarchy such as ours, three rights — the right to be consulted, the right to encourage, the right to warn. And a king of great sense and sagacity would want no others. He would find that his having no others would enable him to use these with singular effect. He would say to his minister: “The responsibility of these measures is upon you. Whatever you think best must be done. Whatever you think best shall have my full and effectual support. But you will observe that for this reason and that reason what you propose to do is bad; for this reason and that reason what you do not propose is better. I do not oppose, it is my duty not to oppose; but observe that I warn.” Supposing the king to be right, and to have what kings often have, the gift of effectual expression, he could not help moving his minister. He might not always turn his course, but he would always trouble his mind."
More recently, Halsbury's Laws adds an important clause to Bagehot:
"[The Queen] still has the right to be consulted, the right to encourage, and the right to warn. However, she also has the right to offer, on her own initiative, suggestions and advice to her ministers even when she is obliged in the last resort to accept the formal advice tendered to her."
I can only repeat that we cannot know what warnings of this kind the Queen has given to her 12 Prime Ministers, or to what degree those warnings may or may not have modified subsequent events.
There's a perfectly understandable tendency for those accustomed to an Executive Head of State to overestimate the rights and powers of this non-executive constitutional monarchy, and to project onto the monarchy responsibility for the actions or inactions of the state of which she is nominal head. Those powers are very limited.
The queen had a choice. She could refuse to morally support evil and accept whatever came her way from the tyrannical parliamentary government that thought nothing of killing children or she could have chosen to support the murder of children without so much as even a wimper of protest. She chose to do nothing, say nothing, protest nothing, write nothing but her signature. She chose to act as a person with no morals, no principles, no regard for the most vulnerable people on earth - babies.
No earthly crown is worth hell. She chose to support baby killing.
Years ago I was offered a job. All I had to do was agree to a certain statement - I had to say yes to something. I was perfect for the job. The job was perfect for me. To get the job, however, I would have had to lie - and it was an incredibly small lie by the way as lies go. I refused. I needed that job terribly, but I had to live with my conscience. The person offering me the job even said, “I’ll give you a minute to think it over” and told me I needed to change my word in order to get the job. After the allotted time, I was asked again, and refused. The person offering the job complimented me on my morals and then told me I couldn’t have the job. I chose. Elizabeth chose. We all do.