Why did mom allow Libby to sleep with her while waiting for the kiler?
That night, mom knew the killer would be there to stab her. And yet she allowed Libby to sleep with her. This makes no sense.
And it sounded like Libby always goes to her room at night since Ben heard the footsteps and when his girl friend asked who that was, he simply answered it must be Libby going to their mom's bed. So, the mom must have expected that Libby might want to sleep wit her that night.