It's best to watch Sharp Objects twice. The first time, pretend it's just a normal show that can be digested and understood after one viewing. Then, after getting to the end, you'll realize it's not a regular show. It's a Smart Show. Every single scene contains clues that are undecipherable, until you know the answer.
On Sunday's episode, we got an answer. Adora's (Patricia Clarkson) brand of sinewy, sinister sweetness was given a name: Munchausen by Proxy syndrome. Adora purposefully makes her daughters ill so that she can care for them. This condition actually ties in perfectly with Adora's other obsession: image control. "Nothing more laudable than a woman who puts her energy into a sick child,” the nurse who knew about Adora's condition for years tells Richard (Chris Messina). Adora's compulsions have spiraled out of control. She was responsible for Marian's (Lulu Wilson) death and has been poisoning Amma (Eliza Scanlen) for years.