Also possible that she sounds too much like that stuck up...whatever...that in most shows are meant to be at least a semi-antagonist of the main character. Essentially, due to social conditioning through media, the way she acts makes viewers stereotype her into the role vis-a-vis Twilight Sparkle as is occupied by Diamond Tiara vis-a-vis Apple Bloom.
Which both shows a lack of flexibility in the mind of the viewer (for some, it takes two season watchings to get to like her) and the fact that media throws at us a lot of stereotypes*. Kids, at least young enough not to have already undergone the programming through pop-culture, should find her more likable, charming, etc.
* Remember kids, stereotyping is bad! If you do it, you're a knuckle dragging hillbilly who sleeps with his/her cousin.