Your friend attempting suicide is traumatic. It sounds like you are having a normal reaction to a severely traumatic event.

Make yourself go to school even if you can't think. Routine and structure are good.

I understand the severe pain you are in. Is there anyone you can talk to? If not, maybe a priest or minister could listen.

It is not your fault that your friend attempted suicide. It has nothing to do with what's in your head. It has to do with the severe pain she is in. She wants to escape the pain. Speaking as someone who has wanted to end my life before, there is nothing anyone could do to help me. When I hurt, there is virtually no way to soothe me. When you can, let her know that you are there for her. Don't blame yourself (that is also a "normal" reaction though).