As I said above, it's not a single mistake. There are other instances where Sansa chooses Joffrey over her family. She pretty much backs up Joffrey with the whole Arya/butcher boy thing to, which had rather grave consequences.

I don't think she needs to have her fingers flayed at all - but I think she needs a hell of a lot of growing up to do before she would be fit to rule a kingdom, which was the point of the secret.

To me, I didn't quite like her and she seemed like a spoiled brat who pined for the big city while considering all that is Winterfell and her family to be inferior.

I think we saw change at the end, and her telling Joffrey that he will die for what he did after she sees her dad's head on a stake, was an important turning point in her character. There's potential there. I'm talking TV-verse, so I don't know how she evolves in the books. Maybe she already has, in which case I'll gladly take back my words. But TV-verse: she's not there yet.

Oh, and I have nothing against Cat. I think she's one of the most level-headed people in there.