My best friend is being bullied at school and she said she's OK but I know she's not. This morning she was crying and I sat next to her and asked if she wanted me to help her and she screamed 'go away I'm fine!!' at me. She's never yelled at me like that before. Is wanting to kill myself because she's being bullied wrong and selfish?

Oh come on ! How will you killing yourself help your friend? Don't you understand why she is so upset.

Even though she yelled at you, she probably didn't mean it. She is in a bad situation and instead of thinking about killing yourself because she yelled at you, think about how you can help her.
Report the bullying to teachers/parents etc.

Ya, I understand why she's upset but I want to die because I'm sick of watching her get bullied and I can't stop it.
Oh come on ! How will you killing yourself help your friend? Don't you understand why she is so upset.

Most schools have a zero tolerance for bullying now. Tell her to talk with her parents or a trusted teacher about this. If she's being bullied, so also are other students.

tickle is correct. Killing yourself won't help your friend at all. It will just make matters worse.

I would take a moment to feel your emotions a little more closely. What You're feeling is probably impotent rage and helplessness. The phrase, "I want to kill myself," tends to portray a desire to stop these feelings, but since you can't stop them by helping your friend, you want to stop them by killing yourself. Understand what you're feeling and why. You will realize that there isn't any actual desire for death but just a desire to help change something you don't know how to change. While saying such things can deliever your meaning, they often lead to misinterpretation causing all focus to be lost on your friends problem and on your problem which actually isn't a problem.

There is always options and there are always ways to help. Talking to a teacher or guidance counsellor might be the best option for this. It could always be that she's already dealing with this. As well she's probably as frustrated with this situation as you are and might view your interference as making it worse.

Go to your teachers or go to the cops. Just take into account the potential fallout from this all. Maybe she just needs a shoulder to cry on or a strong back to help bear this burden. This can be done without words.

Good luck and becareful with your english.

Many people get upset at being asked how they are, if they are feeling OK, feeling better, or if they need help. There's no quick and easy answer, right?

Next time you sit next to her, hold onto her arm and say you are there for her no matter what. Don't ask questions. She will talk when she is ready, in private. You are there for support, for a hug, for company, to listen, not to do one minute fixes.