It's profane to abuse a sibling.
Anna, Marie's five year old sister, is crying loudly in the middle of the store.
Marie wants to make Anna stop crying.
Marie hugs Anna and tries cheering her up with her favorite song.
Marie wacks Anna's arm and covers her mouth telling her that she will wack her again if she keeps crying.
Marie forms a better relationship with Anna.
Anna tells her mother about Marie's actions which results in Marie getting grounded.