You cannot blame the parents for the choices Casey has made in her life. She’s leagally an adult and knows right from wrong...and did so before and after Caley’s death.
Though parents can and do teach their children how to make decisions and right from wrong, parents cannot make their children do them once they are of age.
MAny children, who have been raised by loving parents go bad, and many raised by cruel parents go good. THEY choose and determine their actions once of age...not the parents.
Casey’s parents and her brother are enablers in much the same way families enable an alcoholic. They cover for her, make excuses for her, perjure themselves for her...what else would you call it? They raised her as well. They are a huge part of the mess.