You can't really say that. You don't know what she has been going through her. It could be something that has happened to her creating a dramatic effect. Plus, she may not be Christian or believe in God, she will never understand. If something bad happened to you (I really need to think of a example.) you might turn out mean. Even if you don't mean it.
This is also online, bullies and all that think it's ok to be so mean online. It's a way that they get to you without even getting hurt or anything. Most cyber bullies can't say it face to face, only online.
In my opinion a good thing to do would be to tell here what she is doing, explain it to her. If she doesn't agree then delete her.
That's also why I think it's better to go to real schools. As in ones with buildings that you go to away from your house. A good way to learn life lessons with relationships and stuff.