Lady Victoria likes to have her presence felt and she felt that this guy did not feel her presence. So she had no choice but to stamp her authority. She did this by using her boots. She trampled and stomped on him with it. But beyond that, she also had him lick the soles until they were clean. The guy never failed to acknowledge her presence whenever they were together.
Lady Victoria was out to dominate this guy and she did that with her rubber boots. The mistress used her boots to trample him and before she was done with him, she also choked him. As he struggled to breathe, she laughed at him and went on doing it. She only stopped when he peed himself because she knew he had gotten to a point where he had to change.