Who is the villain.

She didn't just pour fuel but drove a whole tanker of concentrated gas and crushed it into the flames by specifying the age. If Billi denied, she would add proof as well. 

"You seem to be on a mission to torture your sister mentally. Is it fun?" the system asked her. 

Alix could not deny that she was enjoying it even if she tried. It was her goal after all, to torture Billi as much as she tortured her. A specific memory from her past was evoked when the system asked her that question.

"Do you know that when I was kicked out of my bedroom so that Jing Hee could turn it into Billi's music room I was left without a bed? 

I was told to share a bedroom with that fat housekeeper but she would not allow me to sleep on the bed. They wouldn't even give me a blanket so I had to wrap myself up in bits of clothing for warmth.