I don't know what I think about premeditation before the fact. It seems a lot of things in her life were unraveling, being revealed. No job, stealing, resentment at being a tied down single mother still answering to her parents. She was sleeping with multi guys, so needing affirmation, then latched onto TL. I think it was all pushing toward a rupture with her family. She wanted to party down with the single crowd; they probably expected her to be a more responsible mother while living under their roof. Something happened that made her leave with Caylee, rather than leave her behind. Major battle for control. Was moving into Tony's with Caylee an option?? How mad was she at her mother? If she had a terrible accident with Caylee within mere hours of moving out on her own with her, that has to be the most horrible piece of bad luck and coincidence ever. Ever.
She did what she did and she went to TL's, where she did feel safer and calmer. I think she may have meant to leave eventually, but she liked this little interlude in her life, being a perfect GF, forgetting while she was having fun. This couldn't go on forever with her parents right in the same city, though, calling and wanting to see their granddaughter. I think she had a rough "plan" to leave. We know now the car drop off worked because she lied to TL, and then he left for a while. While he was gone, she got her moral support from being around Amy. She had a man on the line in CA. Maybe she was just going to run. Maybe the car was going to be part of a story of carjacking and kidnapping. Casey would maybe/maybe not turn up again somewhere with a story; Caylee wouldn't turn up. Thinking about this is too creepy, but that's my general idea. A certain amount of going with the flow, but a sort of plan.