I know of no medically approved aphrodisiacs for women.

What may help is, as big said, taking a bit of time off for yourself and your fiance. Take time beforehand to learn what it is that gets you excited sexually and when the time comes, try to bring these thoughts to the front of your mind since imagination can be a very powerful thing. (Maybe even bring a dvd or magazine that you find arousing?) Skin-to-skin contact has also been shown to improve arousal regulation and helps stimulate it.

Lots of foreplay helps too, since women usually find it harder to become aroused than men.

Good luck!