Lady Scarlet knew that this guy had made the mistakes she did not want made but he refused to agree that it was him. So she had to find a way to deal with him and she did it by forcing him to lick her feet and also endure her foot crushing. The poor guy had no choice but to confess and tell her in detail what he had done and how he had done it.
Lady Scarlet believes that it is important to punish people when they have made a mistake because that is when they will realize their mistake and change. She did not want this slave to get used to pissing her off so she used her foot worship to punish him. He was turned into a foot slave and had to lick her feet and be trampled as well. He learned his lesson.