When is dignity in silence ?

 The time when my little sister started bragging about something she got and i didn't ,i wanted to tell her to be quiet but then i would get in trouble. At that time i just had kept my mouth shut because if i made her cry by telling her to be quiet i would be the one getting in trouble.All i did at that point was say cool and walked away and she then started crying because i didn't give her my attention but my mom got mad at my little sister because she was the one that started everything and i dint do anything but say "cool." So being silence is the best thing to do because the other person feels bad because they didn't get your attention.