Friend going too far

I have a friend who is in her early 30's. We often go out together hoping to find Mr. Right. She was going out with a guy for six weeks. It turned out that he was married and living with his wife and children. This was about 5 years ago. She now hates meeting married guys on the prowl. She often hangs around with them all night and disappears at the end after getting them to buy loads of drink. Recently she brought a guy home thinking he was ok. Three days later, after no contact she saw him with children. She hung around and saw him bring them to a car. They all sat in the car. After a few minutes a woman came out of a nearby hairdressers and came towards them. She took out her phone and photagraphed the woman. She waited until they drove off and went back to the hairdressers. She said that she had found a silver ring( showing them her own ring) in the car park and she thought a woman who had come out of their shop had dropped it. She described the woman she had photographed. They gave her the name and phone number of the woman. A few days later the guy contacted her asking for a date. She agreed to a date.
When he called around to collect her I was in the apartment with her. She let him in and sat him down. Then she told him she knew he was married. She showed him the photograph and told him his wife's name. He was shocked. She then told him that unless he did exactly as she told him she would tell his wife. She then spent a few hours humiliating him. She got me involved in it as well. It was hilarious and we had a good giggle afterwards.
The thing is she now wants to contact him and force him to come around so she can do the same thing again. She also wants to get more of our friends involved. I think she is going too far. He might turn violent. She says that he deserves it, he is only a rat. I don't know what to do. I do not want to break up a friendship over an unfaithful husband, but I think she should move on.