I think how she acts makes sense. There's a saying in swedish that goes "björntjänst"/"bearfavor" which basicly means that you do something for someone in good intent but it has devestating effects for the recipient. The saying originates from a french tale by La Fontaine (L'ours et l'amateur des jardins) where a tame bear hits a fly on his sleeping friends face with a stone. But when the stone hit his friends face he died.
She has never been challenged by anything because everyone around her gives way... They have done her a bearfavor all her life, and that actually hurt her even if her brothers wanted to take it easy of good intent. She is spoiled because everyone else spoils her, and we are shown that she is actually not a bad person. Because when her duty called she answered the call. Yes, she is naive in every sense but she is actually a good person because she wanted to help even if she did not have any context, which I don't think you can blame on her but everyone around her that isolated her from learning.
I expect a great character developement.