I don't think I know enough about the situation to have an opinion. Mostly because I am completely biased on your behalf, but realize that the hosts may not be accustomed to having guests, or perhaps your daughter is messier than they anticipated. However, I recommend that you try hard to not show your feelings about it (which you mentioned is your approach as well). Have her write a gracious thank-you note and let time soften the rough edges. The guy in this story should rise to her defense as well, if not, perhaps this is not a viable long term relationship. Take the high road.