Your little sister will tell you things she won’t tell your parents. Never make her regret it.

Being the person a younger sibling comes to is a position you were given, not one you earned. She is testing whether one near-adult in her life will not immediately report her, and the whole thing rests on what you do with the first real secret. Repeat it once and that door stays shut for years.

Keep the small things she tells you, including the parts that seem harmless. If something genuinely scares you, tell her you have to bring a parent in and why, instead of going behind her. Being trusted is worth more than being right about one piece of news.