Throwaway for obvious reasons.

My brother got married recently and he had to deal with my grandma having concerns about his marriage. Mainly the fact that my new sister-in-law isn't particularly religious. My grandma is a devout Catholic and most of my family is as well. She was hounding my brother about how are the children going to be raised, what the ceremony would entail, etc. 

During the wedding I looked into the crowd(I was a groomsman), and I could see she was visibly upset and beside herself since the ceremony wasn't very religious. My grandma on the other side of my family officiated the wedding and just read some bible verses.

Now I am not religious at all, I'm an atheist but I don't like to say it. The last time I told someone close to me my religious beliefs, they ended a 4 year relationship just a few months later. So needless to say, I tend to keep it to myself. 

I'm not currently in a relationship so marriage isn't in my vision right now. I love my grandma, she's a sweet old lady and she's done a lot to help me over the years.

I know that if I do start planning a wedding, that information is coming out one way or another. She may just be upset about a non-religious person marrying into the family, but having one in her family would be devastating. 

Am I an A-hole for not wanting to marry until after she's passed away? She's pretty old but if the right person comes along and I do want to marry them, is that a valid reason to delay a wedding?