Screwball's attitude explained. · 1:03am Feb 26th, 2014
A big question I've been getting regarding my story, The Spears of Chaos: Wrath of Screwball, is why Screwball is acting like such a mega-bitch to Discord. This personality has been seen as a bit weird considering that Screwball is not normally this malicious, and never went against anything her dad said in other fics. Well, my answer to you is the fact that in the story, Screwball had been imprisoned in stone for over a year (Spoiler) and the whole time had been looking forward to getting out and sending Equestria back into Chaos alongside Discord again, only for her hopes to be completely crushed when the Spears of Chaos released her and informed her of Discord's reforming. That disappointment, along with some influence from the Spears of Chaos and a bit of a rebellious phase, sent Screwball into a tragic rage and basically led up to the events in the story.
Hope that helps. :D
Makes sense