Well I can definitely understand the mans reaction and the duty that the girlfriend displayed, as it was a warm gesture, however considering they were not the host of the party it was somewhat inappropriate. I personally would have served my man, then asked if he wanted me to get something for his friends, as to show him respect in front of his friends. I would have allowed him to ask them if they wanted anything then I would have went.....Plus to be honest if I am not the host I will not be serving anyone but my man and myself, unless of course he asked me to get for his friends.