Who is Second Friend Who Quotes Scripture from A Grief Observed and what is their importance?

Another friend points out to Lewis that even the Son of God Himself felt distance between himself and God as a part of His earthly sojourn when, from the cross, he asks, "My God, My God, why have You forsaken Me?" Lewis finds very little comfort in that shared experience, however, wondering to himself whether God is just out to play a series of cruel tricks on His children, this one having its punch line at the moment when an innocent Jesus was being killed as a faithfully executed act of love.