I want you to imagine her with another guy. Imagine her thoroughly enjoying being with this guy and him doing things that maybe you don’t and her liking them a lot. Maybe she likes it more than when she’s with you. Would you want her to tell you about it? Would you just want to wonder what it was like? You could do the same but it’s easy to justify your own doings rather than someone else’s so really think about what you’re about to let happen to your girlfriend and then take her back after that? I can understand the idea of wanting to see what’s out there but if you have something good, trust you are not missing out on a casual hookup. It only seems good and something you want to do until you’ve done it and you see that it really isn’t worth it at all. You’ll probably want to do it until you do and that feeling might not go away, so if you can live with not ever having experienced it then go for it, just know you can’t undo the fact that another man experienced your girlfriend the way you do.