OK, let's clarify. This sneak peek is from a Fairytale Land flashback to the days when Snow was still a young princess who hadn't suffered the loss of her mother. But yeah, it turns out she was a bratty young princess.
The sneak peek begins with one of Snow's family servants (guest star Lesley Nicol) trying on Snow's tiara, presumably imagining a better life for herself, as servants inevitably do in this kind of story. Unfortunately for her, Snow catches her in the act, and gets indignant in the way only a child can. "How dare you?" she declares. "That's mine. It's not for a servant."
Fortunately, Snow's borderline saintly mom is there to set the little princess straight about the ways of ruling right. "It doesn't matter if one is a servant or royalty," she admonishes. "Everyone in the kingdom deserves our love and respect."
Well, at least we know where Snow gets her good heart and unshakable morals.