My parents have no idea I'm Atheist because they wouldn't take time to LISTEN to me as to WHY I'm Atheist. They'd just flip and start demanding things of me ( like why, which, they wouldn't listen to so I don't bother. )
If your grandma disowns you for believing something different, I'm sorry but, I can't help, because my advice to you is to tell her politely but if she can't accept it - ******** her. She sounds like one of the many people who helped push me to Atheisim. I can't stand how Christians think we HAVE to convert others. If they wanna believe - fine. Quit shoving it down my throat. (( That's not to say that's my main reason, I've got about a hundred ))
Anyway, I wish I had some simpler or easier advice but I don't. Either she accepts you or she doesn't. I should probably take my own advice here: But lying to her about it isn't good. She has to accept YOU for YOU. Why am I not taking my own advice? Alot of reasons.