One thing I've noticed that my daughter does is that she treats people that are not her family/friends/teachers sort of like flies she can't be bothered to swat.
She is a for-real salt of the earth person in that she's honest, responsible, benevolent, etc, but she does not suffer fools gladly so not everyone gets to see how great she is.
In middle school, she had a reputation for not responding at all when people she didn't like (and I don't mean that she necessarily disliked them, either) spoke to her. She might look at them for a second to identify them, but that's all.
People don't always know how to take that kind of thing. I think it's pretty hilarious, though.