Never heard of one in Naas, but there is one in Baldoyle - not sure if that is out of your way. The staff there are really nice and the dresses were lovely (when I was there 2 years ago anyway!!). Really good prices too
The Sunday Tribune has an article on Bridal wear and it mentions that Barnardos in Dun Laoghaire have a 'Brand New' wedding selection. They get samples, end of season and end-of-line stock from wholesalers and retailers. Their wedding boutique offers the same personal and professional experience that you would get in a regular wedding store without the high prices.
Thanks loads for all your suggestions! I think she has seen one that she really wants so we mightn't have to go looking now but we have to find bridesmaids dresses yet so we might try some of the places you've mentioned.