I don't think you told her the "right" way. You have to learn to control your tone, but learn to tell it to her in a straightforward, matter-of-fact way to show her that it's serious. Look at her dead in the eye and tell her that it is something that's important to you and that you are dead serious about this issue. And she has a choice of either listening and trying to understand your point of view, or leaving.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.