lisa wore a devil suit once that i would love for her to wear something like that again ... only trouble is she was about 10 when she wore the devil suit so she'd need a new one
call me a spoil sport but i think sexy ones are the ones where you dont have to go to to much trouble so there is no danger of looking like a dork
maybe a normal sexy dress and make up and devil horns or go for the vampire goth look especially if you dont usually dress that way