I don't wear leotards personally but I have a lot of acquaintances doing cosplay. From what I gathered, it really depends on the character and how well made the piece is.

Because they need to prepare wearing them for a full day (in conventions or photo shoots), they often put extra care into making them as comfy as possible. In this case it doesn't look custom made, but it if was, I wouldn't be surprised if the girl sewed a thick lining inside it to protect her and avoid the "wedgie" effect.

In any case, there will always be a part of the cosplay bothering you for some reason, but if you wear it for more than 15 minutes, it's also easy to just forget it.