I don't know: I think Sally is a spoiled brat. As odd as it is even to me, I have a lot more sympathy for Betty who genuinely is trapped by the gilded cage and by society's expectations of her. She has the respect of no one and is so fragile that even a tiny, tiny unintentional slight, perceived rather than actual, is enough to crash her fragile attempt at being a good, ideal mother. Like Don, she only knows what being a good mother looks like, not how it feels. It is clearly something she's never experienced for herself and indeed, has never been valued for herself, rather than for her appearance. I see her as a tragic figure and am hoping that some bits of light and fresh air are finding their way through the cracks in the facade of her mausoleum house.
Sally is perhaps unattractive to me because she's an adolescent but it seems like she's going to wear that adolescent fake superiority and fake sophistication and fake world weariness to the end of her days.