Just try to explain to her, if you are in a mood that you are in a mood. I do that with my children. I let them know that I'm not in a good mood and its not them. Even I can only hope that they understand that when I say that I'm not using it as an excuse but I try to explain that I don't mean to hurt their feelings. I don't generally say things I don't mean to them because I know how fragile children are at the ages and stages they are in but maybe sit down and have a talk with her when you are not in a mood and explain what happens when you get to a point when you can't control what you say. remind her that you would never intentionally hurt her. I hope this helps.