And in that situation, she would invoke her reserve powers and do so. First of all, she would warn the Prime Minister. Then she would appoint a new one of her own choosing to put in place the necessary legislation, and then there would be an immediate general election (the last two steps could be in the opposite order but she would act).
Thank you for your informed insights and comments about the political implications that most of us are not familiar with.
It was so much simpler when the tools of governance were the block, the ax and the headsman.