I'm thinking this too...When you really stop and think about it, it's not very hard to physically overpower a two year old. "Shovel" and "neck breaking" and "chloroform" would seem to be overkill.
Is it possible she was plotting against Cindy? Perhaps Cindy told her in March that if she stole any more money she was O-U-T. Maybe she felt that if some sort of "home accident happened" and Cindy was killed, the house and assets would go to good old George who would never kick her out, and wouldn't meddle so much in her life. Then she realizes that no Cindy also equals no babysitter, so maybe she was going to stage a home invasion where someone kills Cindy and kidnaps Caylee? Then she would be free of the two main "weights" that are tying her down, and on top of that, everyone will say "Oh, poor Casey" and "Oh, poor George", and lavish attention on them - and money and casseroles, and everything else we tend to do when someone loses a loved one.
I'm not saying it was something she was planning...maybe just something she was fantasizing about....
Then on the 15th Cindy discovers that KC stole money from grandma. CA hits the ceiling!! You are cut off!, she says. I am not giving you another dime! I'm not putting gas in your car, I'm not giving you spending money, I'm done with you! Fine! says KC...we'll leave and you'll never see Caylee again...Wrong! says Cindy. If you move out and take that baby away, I'll have you arrested on theft and fraud charges. Then no judge in his right mind would give you custody!
Well that's it. Now she is in an untenable situation. She can't stay because CA is making her life a living hell in her eyes, and all the controlling b.s. is literally driving her insane. She can't leave because secretly she has no job and no money anway, and couldn't support Caylee on her own, and if she tries to take Caylee she's going to jail. The only option Cindy has left her is to find some friends to crash with - and leave Caylee with CA. Casey would never let Cindy have that satisfaction and she's flaming mad that Caylee is usurping her role as the family princess while she is being tossed aside. What happens next is the result of a slow angry burn against Cindy, Caylee and their bond that has been building for nearly three years. She feels no guilt, because in her own mind, CA pushed her to this breaking point. She painted her into this corner and left her no other way out....
Plausible?