Is this a normal phase of development?

DD lately has been talking a lot about death, dying, heaven, and God...she's also not just talking about it but making it a part of ALL her imaginative play as well. For example last night we were playing pretend and she said "Pretend you are the sister and your mommy died and now you are all alone and she is in heaven. I'm God and I will show you the way to heaven." And then she went off on a tangent on how the mommy got sick and died and everyone was sad, etc. If she's playing Barbies / horses / trolls / etc., someone is always dead or dying or sick.

We do go to church every week so it makes sense she is curious about the religion part, but we aren't really sure what we should do / how to respond to her when she is pretending these awful / sad scenarios!

Any tips or books would be much appreciated!