i like betty's character and her storylines are crucial the first time (or 3) that you go through the series. but yeah, when i rewatch, i want office shit. and when i say i like her character, i mean i like how it's written and played. you're not supposed to 'like' or 'admire' betty draper. she's an instrument. she's a reflection. she shows us who don is and to a certain extent, who roger is.
what i really like in her character arc from s2-s3 is that she knows she's mad but doesn't really know why. she wants to be mad because she's quite positive don is cheating on her, but cannot prove it (finds only slogans on cocktail napkins in his pockets). that said, she's certain don is "hiding things from her" and she has that suspicion confirmed when she finds out he has a secret past/alternate identity/name/family, culminating in the gypsy and the hobo kitchen scene, which should've yielded every emmy imaginable.
it's where she is able to turn off the snark "oh i know, you're a very gifted storyteller" to some real empathy "i always assumed you were a football hero who hated his father" and "i knew you were poor, i've seen how you are with money, you don't understand it." we also see this in the scenes with her family, notably her brother, played by the incomparable eric ladin. i actually really like the hofstadt storylines throughout s2 and s3 and could've managed more of it, but obviously s4 went away from all things betty.
if i really put my women's empowerment hat on, i could even say that her s3-s4 arc is equally impressive, because it shows how strong and brave she was to want to get away from a destructive situation and actually act on it, whereas most women of the time would've stayed in an unhappy marriage because of 3 small children and all the money she could ask for. it's when she leaves to be with henry that we get a different pov on the whole thing. he will do anything to be with her - his character (underrated) always reminded me of sterling. a bit older, wiser, and willing to call a brat a brat. but like roger, he wanted what he wanted when he wanted it, and it didn't end well.
don writes her a letter basically saying that if they split up, she'll move on and find someone, but he'll be alone forever. even if he meant that metaphorically (he had to), we know what he really means and how he really feels. don, surrounded by people, is forever alone. always on the verge of panic and running away, not caring what he leaves in his wake.
one of my favorite story turns is how it doesn't take long for henry to tire of betty's shit, and that's the real moment that we know - she's the problem. betty is going to betty. she's incredibly consistent. her mother was a bitch and passed it on. her dad was a hardass who didn't make things better. everything wrong with sally is wrong because of betty.
don, in comparison, is surprisingly empathetic and thoughtful, which is why he's such a piece of talent in the advertising space. don has the ability to achieve perfection, because donald draper is an entirely fabricated individual. and if you were going to invent someone, you'd invent someone with minimal flaws. he had a traumatic childhood, upbringing, young-adulthood. but it never happened. it will shock you how much it never happened.