She needs to be institutionalised or get therapy before she kills some one! She is a danger to society. And your parent needs to face the fact that she is a nutter

To those trolls who said he deserved this, how the **** would he deserve this? He did nothing in this equation

I bet they wouldn't have been as calm if it had been their own bed sheets or maybe a piece of living room furniture. .. Your sibling needs help... If it escalates there's a good chance the house is somewhere on the list =/

Even if you did provoke her, burning things isn't the answer to conflict! Little arsonist.

Sounds like your sister might also be a sociopath, and/or pathological liar.

And parents say they don't have favorites

You should light her bed on fire and blame her. Or you can say she is driving you crazy and what ever happens you are not reliable for your actions

Shit

Set her on fire

Man I'd get so fired up about that.