I say don't do it. It may sound like a good idea and like fun. But most likely down the road it will only lead to issues in the relationship. I don't know many girls that come out of a 3some feeling great about their relationship. They usually regret it.

I would suggest that if you are going to do it.. be on the safe side for a while and don't do anything with the other girl. let your girlfriend understand that you are in the relationship for her and that you don't need another woman. If all goes well with you just sticking with her as she does things with the other girl and SHE suggests something else, then it may be safe. Jaded is right that most girls will come out feeling hurt after a threesome, but this is simply because they feel insecure with their boyfriend being with another woman. From my experience, if you're ok with just the two girls touching and you being with only your girlfriend during this, things will be fine.

Good luck.

good choice, there. if you don't feel right about it, then it shouldn't happen. i honestly admire you for that. i feel the same way about it. i once was really drunk on my birthday and my bf at the time thought it would be fun to have group sex...only his idea was to push me onto my friend and then go down on my other friend...when i started to sober up, i freaked. it was like all he wanted to do was fuck my friend because he didn't do anything with anyone else...so you're a good man.

If you guys both feel secure with it, then by all means. However, I'm assuming it is a new relationship since you posted about a crazy online chic less than a month ago. For that reason, I would not go for the 3some if you plan on having a future with your gf. Its a lot of baggage to get into and no matter how cool a chic is, we will all have those untrusting and self conscious thoughts in our heads about the other girl and if you like her better and if having one gf is enough for you, etc etc