Cersie is on a low right now but her and zombie mountain dude are about to wreck some shit. My money is on Sansa eventually killing her/ having her killed.
Ned screwed Ned. Stop trying to blame a little girl. Arya is the character that will upset me most if she dies
This, plus Sansa was always told she was such a beautiful girl and Arya was told she's ugly. I mean, it's not like this difference in siblings is anything unprecidented. You can see it in families everywhere in real life. One sibling is "perfect" and one is "a fuck up". Also, I think the William/Harry comparison is a really good one. William has always been a good boy and is being groomed to be a King someday while Harry demands to serve time in Afghanistan and play the role of "just another soldier".