Lady Shay had a lot of time on her hands and she had to find a way to deal with it. She felt that the best way to do so was to use her bare feet to do so. So lady Shay turned the guy into a foot slave and she enjoyed torturing him and making sure that he learned his lesson in a way no one else had done.
Lady Shay's husband had humiliated her and she wanted to pay him back in the same coin. She had to show him what she was not a pushover and she would not let him take her for granted. That is why she used her socks and her stockings to trample and to stomp on him. In addition, the mistress got him to lick her bare feet and suck her toes.
Lady Shay wanted to scare the crap out of this guy. She was not really interested in punishing him. All that mattered to her was that she got him to do what she wanted. And that is why she described what she wanted to do to the loser and got him to plead with her not to do what she wanted to do to him. He was scared and she achieved her aim.