Considering that, if I recall, the Fairies are supposed to be (yet again) kidnapped in G&G, isn't it more likely that these are the clothes the kidnappers are forcing them to wear? Like how
every kidnapper has, thus far? Considering Mothra's egg washes up in France, I'm assuming the "gangsters" in the title are French - and, thus, the clothes they force the Fairies to change to are going to French-styled.
Chill out, people! It all makes sense if you take a few minutes to think about it.