I don't believe that it is all CA's fault. Parents only have so much control and as you say KC was an adult. However, it sounds to me as if they knew that she lied and stole money long before Caylee went missing and it does not appear that they tried to do much about it while they were still able to. That is before she became an adult.
On the other hand, even though she was an adult, she was living under her parents roof and so they had the right to hold her to their rules while she did. Not to mention that she acted like a spoiled child and was treated like a child a lot.
Well I got lost and missed my point completely. the point is, when you are parents you have to present a united front with the kids during praise or punishment. It sounds like they did not do that. KC learned that she could get away with a slap on the wrist from her mom. She learned that her mom would defend her against her father and that she would gloss over anything that she did wrong. She most likely was the cause of many arguments between CA and GA because one wanted to make her take responsibility for what she did wrong and the other just wanted to pretend that it didn't happen.
Sometimes your child turns out bad no matter what you do or do not do but I think that how she was raised and how they reacted to her bad acts is relevant to a discussion of her actions and how she is.
You wish that everyone would stop blaming her parents for her behavior, I wish that everyone would stop ignoring the behavior of her parents but I don't go around telling them that. There is grief and denial and then there is spitefulness, cover-ups, and lying. Each of us sees something different in the A's behavior. It remains to be seen which of us ends up being right but I have a right to voice my opinion just like you.