Death isn't a punishment. It hurts and makes us feel sad but it's a core part of life. The only thing we are guaranteed in this life is that we will all die eventually. Good people die. Bad people die. Children die. Sometimes even newborn babies die Everyone dies eventually. Her death isn't a punishment to you, your dad or her, it was just her time.
You seem to have a lot of ideas about punishment and curses and family wrath and all that. Your dad couldn't visit her because of his immigration papers and now you think you're being punished with her death because he didn't go to see her. Brother, with all due respect, do you really think Allah kills people because their brothers didn't sort out their immigration papers? That's not how the world works. If something as small as not doing immigration papers results in this sort of worldly punishment then why are people like Donald trump and George Bush still rich and living such a good life?
Life just happens. And it's difficult and scary and sometimes it's good and sometimes it's bad and sometimes it's sad. Don't attribute to curses what could easier be attributed to life and happenstance. I think you would benefit enormously from therapy and grief councelling.