Goddess Nemesi felt that this slave had to be punished for what she had done and that is why she did what she had to do to torture as well as degrade her. She used spit torture to do it and it was super humiliating for the guy. He never saw it coming and he regretted what he had done. He cried but that did not stop her from what she was doing.
Mistress Nemesi needed to put this slave in his place and she did this with her femdom spitting fetish. She had to torture him and she had to degrade him. He had to learn his lesson the hard way and that is what she exactly did to him. The guy knew that she would never let him get away with it and that is how she cruelly punished him like never before.
Goddess Nemesis was tired of how this old client always inconvenienced her. He was trouble and she had gotten to a point where she did not want to have to do anything with him. So she had to humiliate and torture him so she did that with her spit. That was to send a warning to him that if he did not stop inconveniencing her, he would have himself to blame.