IMO it's your right to write a review or not. I believe many people gained benefit from this informative forum, but part of them haven't register an account or chose not to share (reasons can be varied).
For the moral aspect, if people like discussing in this forum and do get useful info, then they should write something down for return, no matter a review or answer few questions from other, that can be a lot of helps, especially for first/new punters.
About your concern of favorite girl becoming famous, that shouldn't be bothered. If I were you, I will never worry about that. People have different preferences, so same girl for them can be neutral or even negative. Even the girl does become famous and you really fancy her and want to visit her frequently, then just tell her you wrote a review about her which potentially brought her many businesses, I believe she certainly will express her gratitude for return (can be better services or much more flexible time than other punters etc.).