Agreed! I loved this show though it wasn't the easiest things to binge watch. I've never seen a series analysed using Dramatica so I'm not certain how the whole assignment works, but I agree that the three most prominent candidates for MC are Madeline, Jane and Celeste.
Not sure if their personal issues all are in the same throughline though. I can see Jane and Madeline occupying a similar Domain with regards to their perspectives but Celeste is a harder one to pin down.
Is the Series OS about the investigation itself or about the fact that it's about a school parents all living in Monterey?
I agree that the MC Style is Holistic, none of them seem to be thinking linearly in terms of cause and effects. I think they are all Changed MCs as well.
Also what made you think that the women were not ICs for each other?