Go with your original intuition!! Although #6 is my favourite photo out of all of these, I don’t think its a photo for the cover. I find it a bit busy, I feel it would put a percentage of people off reading the book and it still follows the same things the lady observed in your original pick. I find #3 is enticing, it leaves you curious, wanting to know more. I believe #3 ticks all the boxes of what you stated you desire in a cover. In #6, as far as a cover, your eyes don’t know what direction to go… there isn’t a focal point. In #3, your eyes naturally follow the flow of the title to the beautiful body.