It's as simple as you asked it. You said you know she would never screw around with other guys, so you trust her. The problem is you don't trust the guys...With that said, it's like in the back of your mind you know that something like that happens, especially if it's a woman (without a man) and with her friends, in a club, you should know things happen, so that's probably what bothers you. Personally, I think yeah it's cool to let the girl have fun once in a while, nothing wrong with that, but she also needs to be mature about it. Why go to the club when you have two children already, and been married for three years. Sounds like she still like the nightlife scene. A mature person (not just a woman) would consider how life is now, will she still be clubbin' when she's 50? Things you have to view are there dude, just reflect upon it.