My wife [27] had her coworker grind on her at her birthday party.

Hey, so last weekend my girlfriend had her birthday and invited some friends over. One of the guests was one of her male coworkers. I knew they were close, but I didn’t expect them to be that close. As the night went on many guests were leaving since they had to get up early the next day. One of the last guests was her coworker and her best friend. They all began dancing while I was sitting in the couch. Her coworker was wearing some pretty loose pants and they began dancing very close. They were both very drunk. I didn’t drink much since I too had to get up early the next day. At one point I saw her facing him with her ass and he began grinding on her. With his loose pants I could see his cock rub on her pants. Then she turned around, and I guess she thought I wouldn’t see or they just didn’t think about it since they were drunk. They were dancing very close again and she began touching his cock. He closed his eyes and had his face on her neck. I think he then noticed that I saw them and he began to move away from her and he quickly sat down. I’m sure he was rock hard. It did turn me on like crazy. But I haven’t talked about it with her. I can’t get the image of his cock rubbing on her out of my mind. How can I continue now and get them to go on?