Marian has been a specter in the background of Sharp Objects since it began, both literally and metaphorically. Her small, ghostly form can be spotted in the background during scenes set at the Crellin house and surrounding woods, proving that she was never far from Camille's mind. Viewers know that Marian died when Camille was young, but what did Marian die of on Sharp Objects?
Warning! Spoilers for Episode 7 of Sharp Objects
At first, it seemed like one of Marian's mysterious illnesses might be responsible for her death. The show was never particularly clear about what was making her sick, but she was often bedridden and suffered a seizure at one point that might have contributed to her passing. But "Falling" raised a different possibility. Working on a tip from Jackie, Detective Dick visited with Nurse Beverly van Lune, who had cared for Marian before she died. And she had some interesting information to offer.
According to Beverly, Marian was passed from doctor to doctor, which resulted in different doctors diagnosing her with different issues. The list was long: they suspected Marian of having Crohn's disease, heart palpitations, respiratory issues, gastrointestinal issues, and renal issues. There was no singular diagnosis to point to what caused her death, but there was someone who might have been responsible for all of it.
The nurse told Richard that she kept a copy of Marian's records because she suspected that the information might be needed again one day. She explained something called Munchausen by proxy to him. Munchausen's is a mental illness in which a person makes themselves sick for attention. With Munchausen by proxy, a person makes someone else sick so that they can take care of them and save them, which gets them attention for being so heroic and caring. Beverly noted that mothers can often have this.
Richard began putting two and two together. He asked if she believed Adora Crellin had Munchausen by proxy, but the nurse sidestepped stating that directly. She did bring her theory to the police all those years ago when Marian died, but all that resulted was she lost her job and then the cops buried it. If the police were so eager to bury Beverly's findings, it seems like maybe there was something significant enough to warrant being hidden. Vickery has gone out of his way to protect Adora before.
Richard tried to bring it up with Vickery, but he didn't get anywhere. Vickery dismissed it and seemed to get angry at Richard, telling him to focus on solving the murders of Ann Nash and Natalie Keene. But of course Richard did not do that; instead he searched through more of Marian's old records at Woodbury Hospital. While he was there, he found Amma's, which pointed toward similar repeated visits and varied illnesses.
It soon became obvious that Adora very likely did have Munchausen by proxy. Early in "Falling," viewers saw how she was dissatisfied that Amma wasn't sick enough to warrant special care. Amma woke up a little hungover but felt fine, so she wanted to skip her mother's homemade medicinal concoctions. Adora manipulated Amma into drinking some unknown substance despite her resistance, and Amma was much sicker later in the day. She'd gone from a little tired to feverish and sweating. Adora had also tried to "take care" of Camille in the past, but been repeatedly rebuffed. And Camille was never sick like Marian and Amma were.
It appears as though Marian's death, while strange and almost unexplainable at first glance, was actually the result of Adora forcibly making her ill. She made Marian so sick that she died, through a combination of pills and medicines that she was not supposed to be ingesting. Jackie confirms as much to Camille at the episode's end. But "Falling" finished without a resolution, so viewers will have to wait and see what Camille's next step is.