Mistress Lilli was not ok with how her boyfriend had cheated. She had caught him cheating and even though he said it was that one time, she could not help but wonder how many other times he had done it. So she trampled his balls to make him realize that she would never stomach any cheating again. He was in a lot of pain as she did so and she felt that he had gotten the message.
Mistress Lilli wanted to send a message and she had to do it in a way that would not be forgotten. That is why she used her hot ballbusting fetish to do it. She made sure that the guy was in the pain of a lifetime as she crushed his nuts at first with her hands and then with her shoes and her feet. It worked as she had wanted it to.