MC is lying. There is only one person she would lie for. Herself. I don't think JO or ToC had anything to do with Haleigh's death. Maybe the disposing. I think someone else did it and that person has convinced her that she will be just as guilty due to her involvement with the cover up.
If you are incinuating that she is covering for Ron, think about it, she would have blabbed when he divorced her. I also think she would talk in jail as Ron is going to testify against her. I think she is VERY involved and cannot tell as she doesnt want Ron knowing she did something to his baby girl.