This woman tried to come between mistress Betty and mistress Rada. He did not know how tight they were and how pissed off they were that she had tried to come between them. They had to do to her what they did to people like her. That is how she learned his lesson the hard way and had to endure being spat on as well as degraded by the mistresses.
Madam Mysteria felt that facesitting this guy was not enough. She had to do something extra and that is why she chose to facesit him and then farted on him. She wanted the facesitting to be painful and thereafter, together with her farts, to choke him. That is what happened and the poor guy learned never to take her for granted or to assume things when it came to her.