I have spent my entire life thinking jws were right about no afterlife . It was so sad, you just take a dirt nap. I constantly dreamed of my father, in the dreams he had been resurrected. I did not believe in an afterlife so that was all my mind could fathom. about 2 yrs ago I completely changed my outlook on this and now do believe we have an afterlife.
Whether or not your grandma prodded you on to make sure she had a date on her stone, I don't' know.I think it is entirely possible. Jung talks about synchronicity. http://en.wikipedia.org/wiki/Synchronicity . I once saw a Seinfeld episode where Elaine said to someone 'that is more than a 'big coincidence' .
My kids were very close to their grandma, it is so good you are too. Thankfully you took care of this, something her son should have done..