you can do a lot indeed. Death it's a delicate topic for adults, and for child even more! Her realizing this thought so young, it's impressive, I believe it gives you another motif to be proud of her! No one can know about the future and how it will unfold. Hug her, strongly, make her enjoy the present moment and make feel her comfortable right now. Love is the cure for any fear.

Death it's part of life as the darkness of nights is part of the days. We must enjoy every moment and appreciating what we have instead of desiring the impossible, make us feel much better every day, every moment.