Yeah, that's really stupid of her. I can totally see my sister doing the same thing.

I'd be pissed off too, so I can't blame you for feeling that way. She's such a hypocrite and a liar like my sister. My sister will never admit to copying me unless she gets cornered

I've tried asking my sister why she does this, but she always says "no, I don't do that! Stop lying! You're the one who does it!!!" So, yeah... tooooootally in denial.