You kinda have to remember that RD is Season 3 RD. She is no longer under Faust’s influence.
Faust's version of RD was fairly accurate pre-Season 3.

Well, that was almost two years ago, when she only wanted to get in the Wonderbolts, assumed that everyone who read a book was only for eggheads and wouldn't tell noone about her childhood fears, not even a little filly.
Also we have only seen one episode of Scootaloo as step-sister of Dash, maybe they'll have some arguments like Rarity and Sweetie Belle (well, at least Dash won't use her as a mule, but it's Rarity,what would you expect from her?).