I've changed my theory from Misty trading Haleigh for drugs. I lost my audience on that theory a few months ago!
However, I still believe that Misty resented Haleigh. Haleigh was Ron's heart, they say. And she was either still high or crashing from a three day drug binge and I believe it when they say she didn't want to babysit. I think she was reckless in caring for Haleigh. Because of this lack of caring for Haleigh, Haleigh died. I don't know if they were messing with her, giving her drugs to make her sleep, if Misty got mad at her because she was going to "tell her daddy" or what - but she died in the process.
Then Ron came home. The 911 call was made. I don't know if Misty told him what happened just prior to the call or if she told him later, but I believe at some point Ron was told what happened to Haleigh. Why he kept this a secret? I'm not sure but it certainly has to do with Ron's # one priority - drugs. That is what all of these people in this case revolve around - drugs. And just like any addict, they would go to great lengths to protect their drug lifestyle, even if that meant "dealing with Haleigh's death" themselves. They don't trust the cops. The 911 call was probably their biggest mistake in their eyes.
It could be because of the drugs, but if not, I think Ron's first interview with him crying looks fake. The minute I saw that video I said "Oh, this family is involved". Then Misty's first interview came out where she is pushing out those tears. Oh my gosh, now we all know what she REALLY sounds like when she's upset!!! The interviews of Ron with Misty are so telling. She is looking to him for affirmation to make sure he approves of her answers.
Thanks for reading my long late night post. I still am on the fence about this whole case. This is just my number one theory for now.