Lady Cary wanted to make sure that this guy understood that she was not going to let anyone mess with him and she chose to make sure that the guy learned his lesson in a way that would not be forgotten any time soon. That is why her punishment tool of choice was her high heels. She wanted the pain to get to him and in the end, it did.
Lady Cary was of the opinion that this guy needed to be punished and she did so using her high heels femdom. She wanted him to feel pain and that is why she used the heels. In addition to that, she wanted to tease him and deny him so she did it that way. The mistress teased him with her tits and as he got excited, he was brought down to earth by her high heel trampling.