Are you really seroius about this question ?
If you are serious instead of asking us ask yourself a few questions.
1, Is there a hot looking girl anywhere on earth that you'd rather just be friends with than fuck the hell out of ?
2, How come you havent allready beat the livin shit out of the guy who's asking your girlfriend out on a date,at his place no less.
If your going to give her your blessing you might as well kiss any respect from her goodbye,women love to play that "just friends" bullshit & thats exactly what it is,bullshit.
The truth is that she dont want him as a friend,right now she's dreaming of his fat cock in her mouth,sucks to say that but it's the truth,dont fall for that stale just friends bs,put your foot down & tell her no way,you'll end up hearing how your not her father & that women dont think like men yada yada yada,dont buy any of it,put your foot down or put her ass out.