sit with them. Spend time showing your own love for them and explain that nobody loves them more than Jesus Christ and that he wants to be a part of their life. Maybe talk about experiences that you have had, and how great God has been in your life, and offer them the chance to accept Jesus into their hearts, even if its just to bring peace into their lives. Don't give up easily...there is nothing greater that you could do for your friend- really. I hope that they will find God. Keep praying.