Religion: I'm not going to say anything about what happened or should or should not have been done on either part. Only that while you shouldn't have to feel like it's being shoved down your throat, it seems your grandmother has had a life charging experience and when something like that happens (of any kind) it is only natural to want to share that with those closest to you. If you look at it from her point of view (though her actions seem obnoxious at best) she probably only has your best interest at heart and wants to share something she believes to be good.
Whether you listen to her or not is entirely up to you.
My advice (if you care to read it): If it happens again try a courteous "Thank you for your love and concern." That's it. Nothing else. It acknowledges that she cares for you without extending her grounds to attempt to push further. And it should block further attempts for argument without ignoring her completely. It is extraordinarily difficult to argue with someone who has just told you thank you.
Corruption: I'm sorry, but I have no idea what to tell you. I suppose I'd ask if it would harm you (emotionally, mentally, morally, other) if you did nothing, and figure out what course you want to take based on that. I know that's not much help. :(
Temper: Personalty, I find it very helpful to get some fresh air in the moment. If you can, try going outside and walking around for a minute or two.
I find it helps to walk around the block and pray, but since you've said that's not your thing I'd suggest maybe trying to count your blessings, things you're grateful to have in your life, or something that makes you smile. If you can focus on the positive things for a bit it might help the minor annoyances not seen so bad.
Wishing you all the best ^^