Re: nikah outfit & other stuff from Aroosia Boutique in Lahore
^ i think it depends on your relationship with them and if you think they would mind.
if you think it's in their price range, there would be no harm mentioning that you've heard that they have nice stuff and can they go and have a look for you (maybe make it out like they should check it out for you rather than the stuff they are making for you). if they think the stuff is nice and worth the price, i'm sure you will hear about it and then maybe you can ask.
my MIL is the kind of person who would really mind something like that so i know not to ask. and from what she did with my bhabi regarding her walima outfit, it would probably put her back up enough that she would do the opposite! lol.