Lady Naomi does not like to tolerate any nonsense when it comes to the pace at which she wants things to be done. That is why she chose to use her feet to dominate this guy because he was slow at finishing the work she had given her. She did not have a lot of time so he had to be forced to do things faster. As he got trampled and was made to lick her feet, he found extra strength and he did the work faster.