I think all of CA's statements were to divert attention away from the smell of the car. Keep in mind the day this was all going down, none of them could avoid the smell of that car. CA mentions the smell in the 911 call, but she was probably demanding answers from KC and repeating the fact that car smelled like a dead body. It wasn't only that KC knew where Caylee was but, that KC knew why the car smelled like a dead body. KC at this point probably thought she was busted which is why she didn't run with the kidnapping story in the first place. I'm sure the kidnapping senario didn't make sense to CA, but it at least took her attention off that car.