From crown to the toe, top-full of direst cruelty

I'm not sure what Shakespeare wanted to show us or wanted us to get from the her soliloquy but I can pretty much tell that Lady M is trying to be the man in the relationship. She's the one making the decisions, planning it out, and giving the orders.  In the quote shown above, it shows that when planning the murder, she doesn't even mind being cruel. Most women aren't known for having that personality, much less taking the initiative to plan something so malevolent.