Hey, theory here, guys
So, the night Ali went missing and Bethany died, Jason allegedly saw Cece talking to Melissa, right?
So, for the sake of the argument, let’s assume that Jason actually saw someone other than his sister - either Cece or Bethany - talking to Melissa, and she was wearing the same outfit as Ali.
That means that Melissa knew there were at least two people wearing the same clothes and same hair that night - Ali and whoever was talking to her. So why would she burry this person without checking for her identity when she knew it could be at least two different girls?
So, either Melissa was lying to Spencer in that video and for some reason she wanted Spencer to believe that she buried the girl cause she was trying to protect her - which makes a really convenient story. No one’s the culprit, Melissa was just trying to protect her sister so everyone stop asking questions; Or/And Melissa had some reason to want Bethany dead, and so she did it.
Tl;Dr: Melissa is actually shady as fuck and is lying through her teeth.