I think at first she did. This was premeditated murder.
It took her a few months to figure it out, and I believe she killed Caylee when Cindy pushed her to the brink. Casey knew she would do this at some point.
Casey did an internet search for missing children in March. She wanted to know how to behave when Caylee went missing. (she sure goofed that up :bang
She searched for chloroform on the internet and how to make it in March, also.
She got Zanny's name from the apt complex in April.
I believe she put a chloroform cloth on Caylee's mouth to put her asleep, and then put the duct tape over her mouth, while she was still alive to seem like it was a kidnapping.
Casey then tossed Caylee in the brush near her house. Casey wanted to be able to watch the area, along with being able to say that "she was close".
I think Casey wanted her to be found soon so she could support the kidnapping story, say that the nanny did it and get on with her life. The apt was empty, so she could say that Zanny fled with the child.
She never thought it through. Cindy enabled her for her whole life, and Casey was never accountable to anyone. She assumed everyone would believe her and she could get away with anything.
Very sad.