She knew that Alex couldn't hurt her. Whose death would help her jail situation the most?
Chad and Lori seem to have been convinced that Heather was responsible for the continued investigation because they claim she has a relative in law enforcement. Have not seen whether this is true or not, but even if she does have a cop relative,
that's not how the world works. They both really hated Heather.
Kay and Larry were the main force behind reporting the kids missing, but I don't really see where Larry would be the 3% guy that kept Kay in place. That just doesn't make sense. I don't remember them verbally hating on Larry as much as they did Kay.
Melanie Gibb, while she initially lied for the two, was starting to crack and eventually did come (mostly) clean to LEO. But if she was a major threat to them in jail or not depends heavily on how much they believed Melanie (and David by extension) knew. I think there's a lot she hasn't told but also there's a lot she really doesn't know...
Zulema, depending on what exactly happened to Alex and how involved she was, could make things
worse for Chad and Lori by adding more charges.
Wildcard guess: Sheila and Jack. Reports indicate they have been big Chad enablers but Sheila
did just testify for the prosecution at her son's trial. Maybe Chad asked his parents for bail money to get Lori out and they refused? Chad made a comment in one of the texts indicating he didn't want his parents around (after Tammy died). We haven't heard much out of them IIRC...for all we know, maybe they started thinking, "Wait a minute, these step-grandkids we were told didn't exist are actually just missing and Chad and Lori refuse to give up their location? That's weird..." and stopped enabling Chad.
Just some observations. MOO.