This girl wants to kill me!?

Ok well this girl is sort of an outcast and said there can only be 1 of "her" so she wants to kill the ppl she wants to be like and last week she brought in a knife and gun to school but the principal found them and took them away, but it was a regular kitchen knife so she must have more, but she only got suspended for 3 days!! And she's coming back tomorrow she brought the stuff in and cut herself in homeroom and said she wanted to kill my friend jackie but she didn't actully try because she got called in by the principal and she said she wants to kill me too and she's coming bak tomorrow and I'm rlly scared to go to shool! What should I do?