I have a friend, a very good friend, who's boyfriend of over a year is actively cheating with random girls. This is not something I just heard. It is something that I know. As her friend, do I have an obligation to tell her, or should I let her find out for herself? She is very serious about him, and has told me that she is at a point in her life where she wants to settle down. She has spent a lot of time and effort on this relationship, and I hate to see her waste her time on a lost cause. What should I do?