I really want to slice my friends arm.
That seems like a bad idea. What makes you want to slice your friend's arm?
She's a terrible person. I've been through a lot of pain and misery with her.
It is wrong and illegal to slice your friend's arm. Hurting your friends is terrible, and you shouldn't do it. If you slice your friend's arm she'll probably call the police on you because you assaulted her.
She deserves it.
If you have a problem with her you need to say something. You could bleed her out if you hit an artery. Try to work things out in a non violent way.