But how much of that is Sheryl and how much is the demon possessing her?
To address this question again, after the recent episode, I feel Sheryl is in full control, always knowing what she was doing to anyone. If she was even partially possessed, I doubt she would have had a reaction to learning what Leland planned with Andy's would-be murder of Laura if all of her actions were under the influence of possession. One repeating theme of the series is that Leland prods and cajoles new recruits, but he leaves it up to the person to embrace the beliefs and take the deep dive with action. This is to say, Sheryl chooses what she will and will not do, such as all of the reanimated Andy manipulation, and setting her own daughter up to be a pawn, then victim in the rise of the Anti-Christ.
As of this recent episode, she's choosing--hypocritically--to be outraged about the attempt on Laura's life, yet appear to not care about what Leland and his demon cult intend to do to the entire population of earth through this Anti-Christ-to-be.
Something i'm not too fond of about the writing of David, is that he (rather the showrunners) seem to be tipping off the possibility that he may leave the priesthood, of abandon faith altogether (which would--in part--send the message that the criticisms around him--about his faith--were correct, when many were not, but agenda-driven, just as various things Leland, some subjects of their investigations, or even what Ben will occasionally say). David's questioning (and not in the rational, Sister Andrea manner) and recently feeling "angry" from essentially "leaping" into / viewing the actions of evil people is just that--he's not possessed, but he's behaving like someone who is blaming the job for reactions from temporary contact. I hope he remains steadfast in his faith, commitment, and returns to his 1st season tendency to see to change certain beliefs from within his particular faith.
Then, there's Kristen. Sheesh. It's becoming clear why Leland targeted her: she is so susceptible to supernatural influence from anywhere (or its drawn to her), as seen with the coven. Despite being a psychiatrist, she fails to look within to analyze why she just falls along into so many supernatural connections / occurrences, which could pose a danger to her own life, as well as her family.
Dr. Boggs now reading scripture--but being drawn into building on his demonic story is a curious outcome, since he has no idea that Kristen's daughters are behind uploading his story--which ends with the mother character meeting a gruesome fate. It seems Leland's scheme has a number of paths as options.
Anyway, the season is still intriguing.