Or at least a better singing voice.

I've known some people to complain about her not having enough intelligence or bravery, but I don't think those are things I'd change about her personally, because her lack of intelligence and her skittish moments work nicely with the story (and admittedly I love character flaws).

However, I think I might have had her go through some definite character development throughout the movie, and in doing so, maybe better defined some of her traits to begin with. For example, if I wanted her to become brave during the movie's events, but have her start off without that trait, I would have had her begin as a bit of a nervous wreck. Later (perhaps when the huntsman tells her she needs to run away) I might have had her start to realise how neurotic and panicky she is and admit it to herself. As the story progresses, she would try to start being braver in certain situations while still showing fear (e.g. have her startled when the dwarfs first find her, and show her really having to pluck up the confidence to befriend them). Much later in the movie, she should get the opportunity to show the viewers that she is learning to control herself when she's scared and generally become much braver, but at the same time she is not fearless; she's just learning how to deal with facing fears and remaining calm.

I think in doing this I'd try and better define her shyness/friendliness mix too. She acts quite shy at times but is also a nice person, but I'm not keen on how these traits of hers are written in the movie. So maybe I'd just look over those and show her gradually developing relationships with the other characters, and how her shyness starts to fade when she's around characters she is comfortable with and we see her more outgoing side. That sort of thing.

I don't really like her original voice.

I would change her appearance ..I would love Snow with long dark ebony hair ..I wouldn't change her red lips or white skin because I love these two facts but I would like her to be more delicate and wear more simple clothing ..not to princess styled ...something like a shirt looking material for top , a long simple skirt with an apron maybe and a corset around her waist !! ... If I could pick something else I could change her voice too, it is nice but too high pitched