"the first question that comes from a seven-year-old Japanese child who says:'My name is Elena. I am Japanese and I am seven years old. I am very frightened because the house where I felt safe really shook a lot and many children my age have died. I cannot go to play at the park. I want to know: why do I have to be so afraid? Why do children have to be so sad? I'm asking the Pope, who speaks with God, to explain it to me.'"Ok. Japan is the least Christian first world nation I can think of (unless one counts Russia as first world). This little girl has very likely never heard the Gospel, or about sin, or anything Christian. We need a strong proclamation of who God is, and what Jesus did.
"I also have the same questions: why is it this way? Why do you have to suffer so much while others live in ease? And we do not have the answers but we know that Jesus suffered as you do, an innocent, and that the true God who is revealed in Jesus is by your side. This seems very important to me, even if we do not have answers, even if we are still sad; God is by your side and you can be certain that this will help you. One day we will even understand why it was so. At this moment it seems important to me that you know 'God loves me' even if it seems like He doesn't know me. No, He loves me, He is by my side, and you can be sure that in the world, in the universe, there are many who are with you, thinking of you, doing what they can for you, to help you. And be aware that, one day, I will understand that this suffering was not empty, it wasn't in vain, but behind it was a good plan, a plan of love. It is not chance."Let me start by saying that I am not the right person to witness to a seven year old girl who just had thousands of people killed nearby. You need a nice, motherly lady - not a troll who lives in a basement! :)
That said, there is a nice way to say what I say - not a dumbed down, watered down, or vacuous thing to say - to deliver the truth in love, with full truth and full love.
With that disclaimer, what this girl needs to hear about is sin and God's righteousness, and His demand for justice. How the world is in rebellion against God, and how we must surrender to Him.
That Jesus' death wasn't just a senseless act against an innocent.
That Jesus paid the price for sin.
And, if we turn from sin and trust Him, we can have our sins forgiven.