Please help. Weird things happening on facebook?

[Victoria]

I made some friends from my school. Since, I started hanging out with them, alot of things going on. FACEBOOK. Someone went to my friends account. He/she read ALL the messages I sent her. It's personal. Next day, a girl added me. I never heard of her. Let's call her Ariana. I asked on Facebook if we met before. She said, No bitch I'm a hacker.
"I'm the one who read your friend's messages. I know everything"
I said "Shut up you lying c*nt you know 13 year old can't hack a damn facebook. Or you know her password". (Sorry for bad languages)
Anyway, she added almost the half of my friends on facebook. She's also messaging them. If I block her she said "If u gonna block me imma hack u too" What the hell? HAHAHAHA!!! Do you find this funny or just WTF?