I feel responsible for my sister's death
Why do you feel that way?
I just feel that way, even though I was nowhere near when she had died.
I'm sorry you feel that way.  Have you thought about talking this through with a therapist?  I think it might be good for you.
A therapist? Are you crazy? Talking with a stranger about personal problems is just stupid.
It is not stupid to do that, it is how you get help. There are people who are professionally trained to do the kind of work you are asking for. It is ok to talk about problems you have with them.