Responses
I think that her fear is pretty normal, considering the last people that called themselves her brother’s “friends”.
her fear was plenty valid anyone without enough context would be weirded out by his actions, plus she was just looking out for her brother and didn't want him getting hurt
the fact she expressed her concerns and tried warning him proves that
The sister needs to chill like aren't you supposed to be proud of your brother that he's meet a friend? You don't need to go spy on them