Take the shotgun away from her.
From Create Your Own Story
You shine the flashlight up into Claire's face, and she recoils momentarily, raising a hand to cover her eyes. You reach up and grab the barrel of the shotgun and with your other hand grab the but. You push it backwards towards her, sending her off balance, and as she tumbles, she let's loose the shotgun.
You turn it around and level it at her chest as she lands on her ass.