IMO the bride chose your friend to be a bridesmaid because it meant a lot to her, being asked to be a bridesmaid is a pretty big honour , and one of the jobs is to help keep the bride happy -it is HER big day after all .
I would be worried about the risks of something happening to the dress as well, if something was to happen to it , after the bride has specifically said she can't wear it out , then it could potentionally ruin a good friendship -weddings being so nerve racking and all, and that would be sad .
Besides, by your friend NOT wearing the dress, it gives a great excuse to go shopping ! not that there ever needs to BE an excuse
