'What even in the world!?'
Lydia was unaware to identify what went wrong or how even the guy died right in front of her. The other staff could not blame her because it was impossible to kill someone without even touching them. That's why Lydia was seen as innocent in that matter.
However it was not known to her that after sharing intimacy with Kayden some changes occurred within her. And one of the major ones included the additional perks. The butler died with the excessive absorption of the life force from his body. And it occurred due to the fear he felt towards Lydia at that moment.
She stared at the butler's dead body with a keen gaze and was unable to spot what even happened. Because when she came back home everything was fine as fuck. And there was no sign of any usual activity that's why there was no point in using poison to kill him.