L.C.
Morning,
I completely understand how you feel, because the talking about death is quite depressing to us adults. However, for a child who is just learning they of course don't comprehend the full scope of the subject.
Your daughter's nature to talk about dying and going to Heaven is absolutely normal. My son asks me about death and Heaven and Hell all the time, and we have the same conversation over and over again. But each time, he comprehends just a little bit more of the subject.
So just be patient...if you can. Part of her incessant discussions about the subject is her way of slowly taking in more and more about it's scope. Plus, think of it like this...her talks about it help her to stay close to Grandma in her heart.
Here for you,
L.