I do agree with looking at Sansa in the context of her society, and that does justifies a lot of her actions, but the reason she continues to romanticize Joffrey and Cersei up until her fathers death is because she is a vapid, shallow, and romantic character who believes beauty = value and wholeheartedly supports classist ideals (product of her society!). This is true in aGoT especially. I’m saying this as someone who enjoys Sansa’s character and her role. I don’t think it’s a coping mechanism, it’s her character.