Towards the beginning of this season of Mad Men, in “A Day’s Work,” Sally went to a funeral for a friend’s mother. She had never been to a funeral before, was intimidated and scared by the whole thing, even as she sat on her bed at Miss Porter’s, smoking a cigarette and claiming “I’d stay here til 1975 if I could get Betty in the ground.”

She was sitting in the same spot last night when her step-father told her Betty was dying.

Much of Mad Men has been the story of Sally’s loss of innocence. She has watched her parents misbehave, use their looks and their charms to their advantage. She’s seen them fight with each other and with her step-parents. She caught Don sleeping with the downstairs neighbor, and Marie Calvet with Roger. As a little kid she got drunk in the Sterling Cooper offices when her father took her to work. Sally has never stopped observing the world around her, even when it has upset her, or when she didn’t like what she saw. It’s forced her to grow up ahead of schedule, but deep down she’s still a kid, only 16 in the fall of 1970.

If Sally’s development has been accelerated, Betty’s is arrested.

When we met Betty Draper she was grieving her recently deceased mother, so distraught that her hands shook and she drove her car off the road, with Sally and Bobby in the back seat. When she went to see a psychiatrist he checked in with Don after her sessions, debriefing and diagnosing to her husband, rather than to her. Betty had once had a great deal of potential, with an education from Bryn Mawr and a modeling career, and a skill for speaking Italian. Fitzwilliam Darcy would probably have called her accomplished. But she chose to marry a man her parents disapproved of–a man she didn’t know was lying to her about everything from his affairs to his identity–and move to the suburbs to have his children.

And that left her feeling stuck–stuck in childhood, stuck in her marriage. She couldn’t grow up while still being treated like a child, couldn’t pick her career back up with Don working in the same industry. She had regrets. She had resentments. They manifested as anger and as numbness. She spent much of the first season fascinated by Helen Bishop, the divorced woman down the street. She saw in Helen a choice she couldn’t make for herself, an independence she did not possess.

Even when Betty did eventually leave Don, it was to immediately remarry. Don may not have loved Betty enough, he certainly contributed to her infantilization, but Henry loved her blindly. He didn’t care whether she was pregnant with another man’s child, or overweight, or whether she was as picture-perfect as she’d been in her modeling days. He didn’t care that she could be petulant and child-like. He directed her more like a parent than a husband, in what to do and what to think and how to raise her children. Betty may have found a way out of her first unhappy marriage, but she didn’t find anything resembling independence.

But the revelation that Betty is sick, and not just sick but dying, with maybe 9 months to a year left if she receives treatment, has knocked Henry down, too. He goes to Sally for help, lays that burden of convincing Betty to try to fight her lung cancer on Sally’s 16-year-old shoulders. He tells her she can cry, but then he breaks down himself before she has the chance. He asks Sally what he’s going to do without Betty when he should be more concerned for how she’s feeling. He drags her home to literally take her mother’s place at the head of the dinner table, with her baby brother in her lap.

And Betty hands her an envelope with instructions for what to do with her body. Ever concerned with her appearance, Betty has already set the dress aside, told Sally which lipstick she wants and how the mortician should style her hair. She says that Henry will be useless and she’s right, he already is, so yet another adult burden falls to Sally. It’s another hard shove in the direction of adulthood.

At the beginning of “The Milk and Honey Route,” before Betty’s lung cancer had made itself known, Sally was on the phone with Don, talking about school, and his road trip, and going to Spain. It’s the only scene in the episode where Sally’s treated like she’s still a kid. Their conversation is friendly, one of the friendliest we’ve seen between them in years, but Don is also very much her father, wishing she had quit field hockey before he bought her the equipment and asking her to sell it, telling her she has “no idea about money” (a phrase that’s not all that different from something Betty said to him once, the way she knew that he grew up poor). It was Don that Sally opened up to about the funeral back in “A Day’s Work,” the “awful” funeral, where her friend’s mother was yellow in a bad wig.

Sally needs a parent like Don right now, someone who can still look at her and see a teenager. Don has worked to be more honest with Sally since the end of season 6, telling her the truth about Dick Whitman, and apparently keeping her informed about this post-McCann road trip, there is more heft to their conversations now, but he still, for the most part, expects 16-year-old things of her. But Don is off in Kansas, sitting at a bus stop 3 million dollars and a Cadillac poorer than he was at the beginning of the season. If Don isn’t coming back, if Sally doesn’t have him to lean on, then what will become of her now?