Hi Melissa,
The authors of three of the four gospels (Matthew, John, and Peter, whose memoirs are written in Mark's gospel) actually knew Jesus and were eye-witnesses of the majority of the things they recorded. If my parents were now to write a detailed account of their courtship, who would discount the accuracy of their story on the charge that the events, only now committed to writing, had occurred over fifty years ago, and that my parents were now very old and, having been married now over half a century, they probably could not remember their courtship distinctly? Are we to think that the years that the disciples spent with Jesus were less sacred and less memorable to them than a couple's courtship is to the couple?
Luke was a companion of these men and other eye-witnesses, and, additionally, had access to earlier written records of the events (Luke 1:1). I have a biography of Martin Luther, written four-hundred years after his death. It is written by a competent historian, and no scholar has ever challenged the credibility of his work on the grounds that it was written so long after the events that it describes. Of course, the author of this book had access to earlier writings, both of Luther himself and of others who wrote about him, as credible sources. Luke's sources were eye-witnesses, which is better than can be said about the sources used by many professional historians.
There is no reason to believe that any of the gospels, with the possible exception of John, were written more than 40 years after the death of Christ (20 to 40 years is most probable). I am only 50 years old, but can readily recount detailed experiences that I had 35 years ago—and a few that were ten years earlier. Yet, I am sure that none of my experiences was as memorable as were the things Jesus said and did, which the gospels record. I would imagine that many of those who saw and heard them remembered those things distinctly until the day they died.
This is especially true when two additional factors are taken into consideration:
1. Prior to writing the gospels, these men had been retelling the stories of Jesus every day since the beginning of their ministries at Pentecost (only weeks after Jesus' ascension). Their audiences had included hundreds of people who had actually heard Jesus preach and seen His miracles, who could well have brought correction, had any of the details been misrepresented in the retelling. Stories so often retold are less likely to be forgotten than stories merely pondered in the heart.
2. (A consideration only convincing to Christians): Jesus promised the apostles that the Holy Spirit would come and, among other things, bring to their memories the things that Jesus had said to them (John 14:26). If we were to suggest that the apostles did not remember these things accurately, then either Jesus lied or else the Holy Spirit did not do His job.
Your friend needs to decide whether, if the gospels were true, she would be prepared to obey them. If the answer is "no," then no arguments can overturn a determined will to disbelieve.
For more on this topic, link to this thread:
http://www.wvss.com/forumc/viewtopic.php?t=404