Yvette's reaction was due to a few factors one of which was her innate hyper sexuality she had never been able to truly satisfy. Another factor was that there was hardly any hope she could resist the urge she was getting when a handsome face such as Evian's was so cheekily grinning and winking at her.
Every action Evian made, every stroke of his cock inside Daria's pussy was performative and a preview of what he would do to Yvette if he ever got the chance.
Yvette got the message clearly. It was why she was finding it hard to quell the shiver in her legs. The anticipation of the pleasure she was potentially in for was taking over every voluntary action she could make.
Had it not been for her ability as a Knight, she might have crumbled to the ground already. As it stood, she was making use of her impressive control of Spiritual energy to keep herself upright.
Meanwhile, Evian kept his eyes on her while he leaned his head closer to Daria's to kiss the Witch's neck.