What do you say?

So I'm sitting in my REL421 class in Flagstaff this past Monday, when the concept of heaven comes up. We are talking about Manichaeism right now, and we were looking at their concept of light/darkness and the eventual pull towards heaven. Usually we incorporate other ideas and stories from other religions (including mainstream Christianity), so it wasn't a surprise when the girl sitting next to me started sharing a story that her "Christian sister-in-law" said to her. Apparently the sister-in-law was attempting to witness to her (or something) and when this girl would not budge, the sister-in-law responded with I'm going to be sad when I am looking down at you from heaven and you are burning in hell. Wow. The entire class was laughing at the stupidity of the comment (coming mainly I would assume from a complete lack of belief in Christianity as well as the absurdity of the comment). The rest of the class I felt terrible for this girl. She does not seem all that shaken up by it, but what a terrible look "Christianity" has in her mind from the stupid comment of one person. It made me realize just how damaged the idea of Christianity is in this world. It is so refreshing and fun to spend time with people who don't believe in Christianity, and yet it is so sad and depressing at the same time. What am I suppose to say in a situation like that? Do I apologize? Do I attempt to show the girl how off-base that comment is from what her sister-in-law should have said? I was just left speechless. I pray for forgiveness in a moment like this. It is my hope and prayer that God will forgive all of us who understand the saving grace of Jesus from the sins we have done in damaging the Name and Being of God. Hopefully I get a good opportunity to start a dialogue with this girl in my class. Not that Jesus cannot restore His own honor, but simply so I can apologize for the mistake made by yet another Bible-thumping, lack-of-grace&love Christian.