Hello Amanda, great questions! I will do my best to help you. First, I have never used the phrase to be "harsh on" something in the way you described. As a native English speaker, it doesn't sound natural to me. I have heard the expression to be "hard on" someone. Some examples of this are: - Please don't be so hard on him, he is only a child. - I'm sorry if I was so hard on you. - The coach was very hard on the players. I would use the expression, "I am harsh to her." because "to" as a preposition can be used after an adjective. Examples using "to" after an adjective are: - I cannot bear people being cruel to animals. - You are so mean to her. - Please be kind to him. It would be okay to also say, "I am harsh with her." The rule is "with" is used to indicate feeling. Some examples are: - I am dissatisfied with the movie. - I am happy with your answers. - Are you angry with me?