PLEASE PLEASE PLEASE PLEASE HELP!?

My friend Jess has been getting bullied by this girl Jordan. Jordan has been getting all of these people to try and beat up Jess and getting other people to threaten her. It won't stop. We can't just *walk away* And no ones parents/teachers are helping with anything. I've told Jordan to just leave it, she won't. And my friend Jess has just been crying, and I've helped her so much, I just don't know how we can stop it anymore. It's gone really far, and Jordan is just such a big *****! HELP