Is it normal to want to want to tell him the truth?

My guy friend said that he likes this girl, yet she has a boyfriend. Supposley he found out that he would have had a chance if he stayed talking to her. he stopped talking to a lot of peoples because he could not afford his cell and keep his car running. I was able to keep contact with him on facebook. She did not even thought they are friends on there.Yet once they stopped talking for about a month she found someone else. She is moving to be with this new boyfriend. He saids that he likes her and her daughter yet he did not say good bye to the daughter because it would be too hard on him.
I do like him as more than a friend but I do not want to see him get hurt. I caught her in a lie. She told me that she will be moving back. So I tried to cheer him up by saying that we will be able to see ya whenever you move back. And she said right in front of him that she was not moving back. I was so shocked. When I heard that I wonder if she is even going to keep in contact with him when she leaves or just don't bother.