(My opinion here, very open to interpretation and not something I’m going to debate.)
I don’t know, I disagree with this assessment. I think you’re confusing cause and effect here. Sansa does lack confidence in her own instincts, but i don’t think she truly lacks confidence as a person.
Maybe it’s one of the reasons she is so eager to fit in the mold, to become the best in what’s asked of her.
This is the cause in my mind, not the effect. Sansa was “a lady a three”. And that was ideal, she was praised for it, it’s what was expected of her. At the same time, what does being a “lady” in Westeros really mean? They are meant to be dutiful, soft spoken, accepting, obeying, second to men, ect. They are supposed to never question anything in some ways.
I think society made Sansa this way. She’s the “perfect lady” in some respects. It’s a good thing in that it allows her to function well within society, be praised and loved for it, but at the same time, it’s harmful.
Think of other female POVs. Arya, Brienne, Asha, Arianne, and especially Cersei for instance think on what Westerosi society expects of women, they acknowledge the unfairness, the limitations, the expectations, ect. Sansa, on the other hand, doesn’t really. We don’t have a moment from her where it’s clear she’s aware and/or upset with the placement of women in society.
Sansa is very content with her place as a woman. This isn’t surprising since A) it’s all she’s ever known, B) she’s good at it, and C) that lifestyle seems to appeal to her.
But I think that manifests in Sansa not wanting to assert herself always. She’s the “good girl” who does what’s expected of her. And oftentimes, what’s expected of her is to just take whatever’s being handed to her and told to her and just accept.
Compare Sansa thinking to herself how she never considered having a claim to Winterfell because she had three brothers to Arya asking Ned in AGoT whether or not she could be the lord of a holdfast. Sansa accepted how life was for her, it’s something that resulted in continuous love and praise and affection because that’s how women are supposed to react. Ned, who had Lyanna as a sister, seems conflicted. He loved and respected his sister, but he also believes to some extent that her wildness got her killed. But ultimately, through his comments like “the impossible task of making you a lady” to Arya, we can see that Ned also goes along with the system for the most part. And that’s why Arya’s self-esteem is so poor even though people think that Ned was the cool parent or whatever. He was better than most, but he was still accepting of the system overall. And Arya failed the system in the beginning of the story.
So with Sansa, to me, it’s a partial manifestation of her lady training and how she was raised.
She questions her instincts on certain things because she was raised to believe that what she’s told by authority was right, it was the truth, that was how things were, and she was accepting and okay with that. Remember this moment in AGoT when Sansa tried to question Ned’s authority directly:
“Sansa, your lord father knows best,” Septa Mordane said. “You are not to question his decisions.”
This is the sum of it. Sansa is “eager to please”, and pleasing for a lady is often abiding by whatever authority figures (almost always men) tell her to think, feel, say, do.
When her life went to hell, it was still expected of her to just take whatever was dealt to her, but now it wasn’t sheltering or not having privileges her brothers had or anything relatively innocuous (comparatively,) now Sansa was supposed to take abuse, reformations of identity, being an accomplice in murders, unwanted marriages, denouncements and mockery towards her family, ect.
And that’s one of the reasons why I think Sansa’s development involves learning to trust her instincts and question. While there was nothing wrong with her being a proper lady by Westerosi society, it’s no longer an option for her to completely fall into that mode for her if she wants to gain agency. The authority figures in her life, the people around her seeking to control her, none of them have her best interest at heart. Sansa needs to assert herself for herself.
The cause is that Sansa is eager to fit the mold, I think. And the effect becomes that part of fitting in and people pleasing meant never questioning, trusting authority and not her own instincts. As as result, she became accustomed to accepting that her instincts were not the ones to trust, whatever authority was telling her was.
So anyway, that’s how I’ve always interpreted it as. It’s not a lack of confidence in herself so much as something that’s been drilled into her head since she was born.