The most important thing I can urge you to do is to pray for your friend, that God will open her eyes to His truth and help her understand her own spiritual need. Some people, I'm afraid, don't really want answers to their questions; they only use them as an excuse to avoid God.
Let me suggest two answers you might give to her question. The first is actually a question: Does she believe there is such a thing as right and wrong? Is it wrong to abuse an innocent child, for instance, or to refuse to help someone who is starving? I suspect she would agree that these are wrong—but if so, then shouldn't we expect God to judge those who do them? Does she honestly believe that Hitler (for example) shouldn't be punished for his sins?
But the most important thing you can tell her is that God doesn't want us to go to hell! Yes, in reality we all deserve nothing less than His judgment, for we have all sinned. As the Bible says, "For all have sinned and fall short of the glory of God" (Romans 3:23).
But God loves us, and the proof is that He sent His only Son into the world to die for our sins. We deserve to die for our sins—but He died in our place. He took the death and hell we deserve, and now by faith in Him we can be saved. Point her to Christ, for in Him God's judgment and love are reconciled.