Breaking off contact with 'the other guy'

I have been in a wonderful relationship for 4 and a half years, but last week my girlfriend decided to break off the relationship because she fell in love with an internet friend and didn't think it would be fair to just pretend nothing was going on.

During the last week we both did a lot of soulsearching and she realized she didn't want a life without me.
We decided to stay together, which made me ecstatic of course, and I will be looking for help to help me continue and regain trust.

But, here comes the current issue, the other guy is one of her best friends, and he doesn't have many friends at all. But at this time I can not handle her talking to him.
I asked her to break off her contact with the guy, she was thinking about it as well and agreed.

But now I feel so guilty about it, I know it is logical, and out relationship would most likely be dysfunctional with him there, but somehow I feel I should be above this.

What do you people think?

Your saying you GF decided to break up with you because she fell for a internet/Best friend? After soul searching she decided to come back and be with you?

Well isnt that nice of you..I mean to make it that easy for her to break up and come back when she chooses...You even feeling gulity for not allowing her to talk to the guy she left you for....Nice.

I wouldn't trust her to break it off all my her lonesome if it was YOU who suggested it...

If she stays in contact with him there's a VERY good chance she'll "fall in love with him again".

I dont get it.. so what? the internet guy is the best friend guy??
Make it a bit clearer...
Umm.... Also what the hell is she doing falling in love with a guy online? She might as well fall in love with a computer...
Anyway she sounds a little misleading, but dont start getting all 'i have to follow her' everytime you see her with
a guy friend