I think that’s exactly what was happening: Cindy, especially, did not want anyone to uncover what a monster her daughter was. She’d just lost her granddaughter, and now she wanted to hang onto her daughter, despite the fact that she is a cold blooded killer.
Cindy is the ultimate “control freak”. She is smart, gainfully employed, rigid and proper, perhaps to a fault, (recall she never took Casey to a GYN util she was 19) and Cindy was demanding. What’s not right with that picture? Cindy out performed her daughter, probably her husband too, and was the provider with power over the household, and Casey and Calee. The resentment for these circumstances was screaming from Casey and the incessant desire to escape and party. Add to that Casey’s clinical narcissism and you have a storm coming. Calee paid the price how ever it was horribly done.
I agree with you that Cindy wants to control the outcome, as usual, and spare herself the realization that she is the mother of a “monster” and is dealing with how stupid she was to believe so much fantasy from Casey for so long. Can’t get over that Casey said for two years, she had a job at Universal. Never happened.