Your parents not visiting your dead sister's grave doesn't mean they don't care. They probably had grieve long enough about your sister's untimely death and sometimes visiting graves triggers sad memories no wants to relive.
About being raped and sexual harassed, I am sure you heard a lot from counselors that is not your fault, you didn't asked to be rape, or you shouldn't feel ashamed. Even though you have deal with many counselors who have failed to help you, you shouldn't give up in helping yourself.
Just don't give up. I am sure that is very unbearable on you, having your flashbacks haunted you.
Just don't give up. There are many women who have learned to live pass their domestic abuse experience.