In the European version, they add a brief scene after what you saw. Scotty and his ex are back together, and on the radio is an announcement that the husband was arrested after a manhunt.
Opinions differ on the fall. To me, it seems obvious that Judy felt very guilty, and she saw a shadowy figure approaching her, and her guilty conscience said it was someone or someTHING come to get her and punish her for her misdeeds. She panicked and turned to run. Since she was where she was, there was a chance to turn and take one step before she sailed out into the air...and, being heavier than air, to fall from the tower.
Scotty had brought Judy up to the tower because he wanted to confront her with the truth, and prove he understood- too late- what had happened. She was trying to talk her way out of this (out of guilt, etc) when they were interrupted.
A lot of people, if fleeing, will not allow themselves to be backed into a corner, they will keep heading for empty space and away from a corner. Scottie wasn't brought up on charges because he didn't commit a crime- except, perhaps, trespassing.