you need to have the cursed item of werewolf on you since her attack will not do any damage to you apart from the grapple attacks. you also need to have at least 25 - 30hp for the full corruptive transformation. you'll know when you've got it because your skin tone will change to match the werewolf. also you'll need to have been unbirthed by her prior to it for the full effect with the Btch collar