The WDW version of Snow White's Adventures was modified to make it less scary (and the word scary was added to help parent know that it really was, actually, still a good bit scary). The
Disneyland version remains generally the same as original.
In the original attraction, you were supposed to be Snow White, going through the adventure. The witch offers you the apple, you wind your way through the forest, etc. That's why Snow White didn't really appear in it.
To less "scarify" it, Snow White was actually added to the attraction in several places. But, still, many scenes are dark, loud and a bit ominous.
That said, I'll play the somewhat broken record titled "All Kids are Different." Our daughter never had a problem with Snow White. She began experiencing a few months before her second birthday. But, she got aclimated to Disney attractions early and often and seemed to be able to begin drawing at least a faint line between "reality" and "fantasy" at an early age. Not so much as to ruin the Magic, but enough not to be overly scared when it wasn't necessary.
But, indeed, many youngsters are scared out of their wits by the attraction.