I'm happy my grandma died
Why would you be happy your grandma died?
Because she was a mean bitch that made my mom suffer
Even if your grandmother was mean, you still should not say that you are happy that she died. While it may be a relief that she is gone for the sake of your mom, death is of family members is never anything to celebrate.
I can't fucking help it but I'm happy she is gone. It's like I'm glad she is suffering in hell.
Are you honestly happy at the thought of her suffering in hell? If so, I think you should seek some therapy. Maybe you have some deep-seeded issues that you need worked on.