Lady Tassia loves a good foot rub and that is what she wanted today. But she knew that her new slave did not know how to give her the kind of rub she wanted. So it was up to her to teach him what she wanted him to learn. That is why she chose to make him learn how to lick her feet, how to rub them as well as how to worship and pamper them.
Lady Tassia needed to make sure that this guy was degraded. She had to make sure that she taught him that she was not going to let him get away with anything bad. But if he did well, she was also capable of rewarding him. So she both had him lick her feet and gagged him and then she gave him a footjob to show him what she was capable of.