I would think there would still be something which could tie Misty to Haleigh's disappearance if she were responsible. (She isn't smarter than another known suspect where the evidence was all over the place, imo.) For her to carry out even a soft kill and dispose of Haleigh, she would have left some clues along the way. There HAS to be something there! LE has overlooked it (proving they are incompetent) or nothing took place at the home and the entire thing happened somewhere else.
For her to have any ties to Haleigh's disappearance, all one would need to do is determine whether her story holds true. Even the confusion of sleep into panic can't explain why her mind hasn't solidified her story. She has now admitted to the inconsistencies, so we can all agree that her story doesn't ring true. If her goal was to help find what happened to Haleigh, her method to attaining that goal is simple: TRUTH. She, in admitting to the inconsistencies, and being asked why, adds another lie: "I don't know." Yes, she does. Everyone knows why they lie. First rule of lying is self-protection. But what is she protecting that she cannot allow anyone to know? And why at that juncture, knowing that she's just admitted to having been inconsistent, would she continue to be evasive?
People in stressful situations are "allowed" to be scared and confused and not a little terrified about what's going on. Add her age onto it, and it could have all been explained away with "I was so scared and I was just trying to figure out what MUST have happened because I just don't know what happened." That would have explained it all and given at least 1/2 of WS'rs validation that their theory was right about her and she's just a frightened little girl who finds herself way in over her head. Somehow she feels this option is not available to her. I will guess, though purely speculation, it was eliminated as an option because she wants to appear responsible, older, and "grown up" to everyone.
The next possibility for inconsistencies is that she was chemically altered. It is not a claim to know she was, it is an option to explain. She parties, passes out, finds Haleigh gone and, because of her age, cannot admit this to the police for fear of punishment. One would hope that she would get over that pretty quickly, understanding that the situation is grave enough that a petty charge of MIP would pale in comparison to knowing what was going on in the hours before Haleigh went missing. But she feels this option isn't available to her, either. I will guess, again pure speculation, that if this is the case, it is because she knows how Ron is. Not only will he blame her, but all her dreams of being Mrs. Ron will go down the toilet and she'll be out on her ear. He is not readily reasonable, though perhaps he can get there given time. But this is his daughter, and it's hard to believe that there would be any situation that would suggest he would be reasonable, yet inexplicably, Ron not only listens to reason, he proposes and marries Misty. Now the other half of WS'rs are convinced that their theory is correct, and Misty and Ron have a shared interest in the story. IF Misty was chemically altered, Ron will be (rightfully) pursued by DCF for leaving his children in the care of a minor doing illegal substances (alcohol is considered an illegal substance as well due to her age). Ron stands to lose an awful lot, as it turns out. Suddenly, they're tied together in a complicit agreement to keep part of the story hidden (we don't need to be looking at what he does in his personal life, remember?). Then we get into whether Misty was actually home or not. All in the last paragraph still applies, since they each have as much to lose. Does that mean either of them had anything to do with what happened to Haleigh when she disappeared? Not at all, other than that they keep part of the truth that protects them and they believe doesn't add anything to the story that Haleigh was taken and they did not do it. But it DOES matter. Truth, no matter what has to be revealed about the adults in her life, is all that will help bring Haleigh home.
The question of "What happened to Haleigh?", then, is IRREVOCABLY tied to what the two adults in her life do with their personal life.
I'm just saying the very slight shift in her demeanor since the ring, could possibly indicate that this is what was going on.
