I’m rewatching the series and the first 5 episodes Sheryl was a great grandma and loyal to her family. And then on episode 6 with the prophet, who tells Kristin to avoid red for 7 days, is where Sheryl ends up having s-x with Leland and there’s fire around them symbolizing her having relations with a demon since David says he believes Leland to be a demon. Sheryl is wearing red lipstick in that episode and after having relations with Leland, she goes to his closet and grabs a red dress. I feel like she became evil or became possessed after sleeping with Leland?
Never mind just watched season 3 and I think she’s Evil because she had the chance to have Leland exorcised and instead she helped him recover.
She also tells Leland after their breakdown that he's not her first demon, so she's been a least evil adjacent in her past.