Allison did NOT kill Mona. It's most probably Cece or someone wearing a blonde wig. Prior to this scene, you could never even tell if A is male or female. Maybe Allie has something to do with the murder but that's a different story.
Don't forget that during the Halloween episode happen supernatural things.
Maya's
comeback maybe just one episode this time.
Can anyone explain me how both Allison and Bethany were buried - were they in the same grave but in different time?