I am truly sorry for your friend. Obviously he has been cheating with this other girl for a long time.
I always give girls advice to have more in their lives than their guy, so that when things happen, they are not totally devastated.
She should talk to you about what she really wants to do. maybe there is something she was putting off because she was with this guy, like a class, or hobby, and she should use this time to pursue it. She will need to date someone else, but at this time she may not be ready.
If she is ready, eHarmony, or better yet, she could meet someone while pursuing her own hobbies. Those meet ups become the best relationships.