This mistress could not let this guy continue being unaccountable. He had to be punished for the nonsense he had been doing and that is why the mistress chose to use her fisting femdom to punish him and teach him to be accountable. She made sure it was super painful and by the time she was done fisting him, he had felt the pain of a lifetime and he changed.
Mistress Barbara and her friend had agreed to do certain things with this loser but the loser did not do the things they had agreed on. And that is why she chose to degrade him and to punish him so that he learned to honor his word. She did not want to work him again if he was untrustworthy and that is why she fisted him cruelly in the ass.