FSIL sent me a picture of a dress and I assumed that she was showing me it because she made it (she is an intermediate sewer and her talent continues to grow each time she makes something). When I said 'wow, you made that!' she revealed that it's actually a dress she bought for our wedding.
Our wedding is very formal and will be black tie and what she sent me is not close to it. I don't want to be the 'black tie police' but what she has shown me is not formal let alone black tie - it's something I'd pick for maybe a smart-casual wedding.
Her husband (best man) will be in a tux with a bow tie and I feel like she will be a bit out of place. If I say anything to her, I would try be really casual about it - i.e. something like "I'm not entirely sure that it is black tie but it looks so comfy!" but I really don't know, do I tell her anything at all or just leave it?
EDIT: Having thought about this a bit more, I have decided I will wait until we discuss her husband's attire (as best man he will be in a rental tux that we will decide on with him) to slide in something to the effect of "yeah since the wedding is going to be so formal and with the black tie dress code we've decided on tuxedos, won't they look dashing" . I think this will be the best way to give a subtle hint without putting her on the spot. Ultimately if she ends up wearing the dress she showed me, I am totally fine with it. I think she will feel rather under dressed (a la Elle Woods at the non-costume party dressed as a playboy bunny) but that is something I can't stop or dictate.
