That's where you are wrong. You perpetuate her victimhood when she knew that he wasn't single but chose to believe his lies because it made it easier to be less hard on her own conscience. She is just as much to blame for this as he is. She is the one that didn't get the morning after pill when the condom broke, she is the one that chose to ignore her own gut when she KNEW that something wasn't right, she is the one that listened to his lies when she knew in her gut that they were just that ~ lies.
Stop perpetuating victimhood here when she is no victim. Once she started to question him she knew within that he wasn't who he said he was. If she listens to you and takes on the role of "victim" then she is likely never going to learn from her own mistakes.
Yes, he is a piece of garbage for not fully disclosing his status with her. She however volunteered for that role when she ignored her own intuition in order to continue on with him.
Getting vendictive doesn't help anyone... particularily not her. Telling is her perogative but it won't help her in any way at all... so don't state it like it will.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion