I disagree with everyone saying 'don't tell her' and from your post it does sound like you are uneasy about what you've done.
First, presumably she will twig that there is something different about her accommodation pretty quickly and question why, as I'd have thought most of the other students would know this was the option being picked for them or would have picked it themselves.
Secondly, even if being around non-drinking students would be good for her in your eyes and is a better match with her current lifestyle, she might be hoping to reinvent herself a bit or do things differently at uni. I appreciate this might not apply to your DD at all but just raising the possibility (personally my own reinvention plans suffered an early setback when my DM discovered that I'd bought some blue hair dye and packed it into my suitcase for uni... she was not amused by this).
Thirdly, even if your DD is really happy with this accommodation, is there a risk she will resent having been left out of the loop? Are you treating her fairly and laying a good foundation of trust for the future as she takes this big step and moves away from you? That would be my main concern.
My own DD is very young so perhaps I'll feel more protective and empathise with your position more by the time she is st the same life stage. I also appreciate that your DD clearly has needs that make you understandably even more worried for her.
Nonetheless in your shoes I think I would explain to her that you chose to help her get quieter accommodation as thought it would help but have now realised you made a mistake and should have given her the choice.