"courtesy is a lady's armor" is what sansa repeats to herself in king's landing while she's being held hostage and is at the mercy of people who seek to use her as a political pawn for their own gains (the lannisters and the tyrells). it is not meant to be aspirational, it's a coping mechanism which she uses to make herself small and invisible to survive the mental and physical torment being heaped on her by a society which only recognises her value in the form of her reproductive capabilities and expects her to remain a docile object, not an active participant in her own life. and internalising such an ideal begins her loss of identity arc. presently she's sequestered in the vale, forced to leave behind her name and her home, to forget who she is. because that's what it does to you, hollowing yourself out to meet the expectations of feudal patriarchy until your will is broken. catelyn experiences it in a literal sense with stoneheart serving as a metaphor for this process. and obviously what is happening to sansa is not her fault, neither her nor catelyn are being criticised by the text for performing feminity, it's a criticism of the exploitation of young girls by westerosi society, something that is enforced and achieved and passed down through those songs about dutiful ladies awaiting gallant knights in their towers. the key here being that the version of heroism preached in those songs (able bodied, all men, all handsome - a definition which excludes bran, tyrion, sandor, brienne) and the role of women as passive agents is what's being questioned, not the notion of performing goodness in a broken world. sansa is right to be a dreamer, to be kind—that's what makes her a hero. but her arc is also about unlearning those harmful foundational myths of westerosi society.