Lady Scarlet wanted to humiliate this guy and she knew that the best way to do it was to turn him into a cuck. She did this because she knew he would be hurt by that since he had feeling for her. But he had messed up and she wanted to use those feelings against him. So the mistress forced the guy to lick her feet and those of her lover as they had fun as he watched.
Lady Scarlett laughed when this broke guy wanted to hang out with her. She agreed but as he later found out, it was because she wanted to torture him. She did so using her foot cuckold fetish and she dominated him in a way he had never been before. She had him do crazy things such as forcing him to lick her feet and those of the man she actually had sex with as the loser watched.
Lady Scarlet was interested in dominating her stubborn slave because she wanted him to learn never to do things that way. The mistress felt that the best way to deal with him was to do something to shock him to the core so she came home with a man and she had the slave lick their feet as they made out and had fun. He was humiliated and his ego deflated.
Lady Scarlet is the sort of person who does not take things lying down and that is what she did to this loser. The mistress made sure that this loser learned his lesson cruelly by turning him into a foot slave. He had to lick her dirty feet and also suck her toes. She told him that he would soon be ball busted if he did not change and he did out of fear.