I'm so sorry. This is a horrible thing to do. She's a selfish, immature, POS skank. I hope that he can realize that he is much better off without her, and he can move on. This has got to be one of the lowest things a person can do. Please let him know that WE appreciate all that he has done even though she doesn't.
As the saying goes "what goes around, comes around". She'll get hers some day.