let "Simon" (or should we call her "Simone"?) pout all she wants.  She has to learn that you can have a dry and sarcastic wit, and you can give honest advice, WITHOUT being hurtful.  You are being true friends by letting her know that her current tactics are not acceptable.  She can use this as an opportunity for reflection and growth.  Let her know that she is welcome back when she is ready to be more tactful or diplomatic.