Honestly, Final Fantasy MMOs so far have been well toned down compared to some of the more... liberally designed MMOs.
Sexy is a matter of opinion. If you're talking about exposed skin, probably Bard and Dragoon. But Elezen females pretty much have it made when it comes to making any outfit look attractive. They simply got the figure for it.
But if your wife is intending to show the majority of her avatar's stuff while out there fighting - She'll be pretty disappointing. For the most part, armor looks like actual armor in this game, with a bit of liberal design for the sake of fiction.
