Lady Sandy wanted her slave to stop being lazy and learn to use his hands for his own good. He had to be hardworking and she was not going to sit back and watch as he wasted himself because of his laziness. So she hand trampled him with her boots. It was cruel and it was painful but he deserved it and it was from that that he learned to work hard.
Lady Sandy was shocked to see this guy projecting strength she could tell he did not have. He was acting tough and she could not understand it so she called his bluff and she used her hand trampling to test him. He failed the test spectacularly. He cried and begged her to stop it as he could not take it anymore. The guy nearly shit himself as she hand trampled him.
Lady Sandy was pissed at how drunk her husband was. She wanted to wake him up so she hand trampled him using her bare feet. She had let him sleep a little bit and she felt that together with her trampling, he would wake up. But he did not wake up and she found out she had misjudged how drunk he was and how much effort it would take to wake him up. So she let him sleep until he woke up himself.