I may be wrong, but I don't think that @WrongWomen necessarily meant that you should go for a traditional MotB full-on jacket/dress/heels/bag/fascinator get-up?
She probably meant something perhaps a bit more unusual, from a higher-end brand or a lesser-known one, rather than somewhere like Monsoon which - although it may do some nice things - is a bit of a default for wedding guest attire, alongside Coast, Phase 8, Karen Millen, Hobbs etc ...?
(I'd never suggest that kind of stereotypical MotB outfit either. I don't like them & they seem to transform most women into Stepford wife lookalikes. They're also hideously overpriced, usually synthetic-heavy, bear no relation to current fashion &, IMO, those awful shops that sell top-to-toe outfits prey on women's insecurities & fleece them!!!)