I think it's pretty evident the family was well aware that asking Casey any questions about anything was a waste of time AND it probably always ended up starting a whole new melodrama with this brat.
Since there was a baby in the house they probably tried to avoid big blowups the best they could.
Looking back in hindsight, probably the best solution to the Casey problem would have been for them to hire a full time live in nanny for Caylee. Being replaced by a REAL nanny would have either caused Casey to open her eyes & stop being an ungrateful brat or she would have been happy to be 'free' of the annoying kid.... spun out of control & ended up dead or in jail eventually. Casey enjoyed being the center of attention even if it was for negative reasons. If she was really unhappy all she had to do was get a job & move out... like an adult. I don't think she necessarily had an unhappy home... I think SHE was the main reason the home was a stressful place.... and she liked playing the poor victim for whoever would listen.... of such mean, horrible parents who wouldn't babysit 24/7 & who expected her to be a decent mother.
Once they had a caregiver for Cayee and Caylee was happy, they could have fought for full custody & if they won, they could have gotten a restraining order against Casey in the event she was angry at the custody agreement.