hunny listen......
buy her some nice sexy underwear.......if u don't know her size...go to her undie draw and look at the size of her bra's and knickers...if it's an all in one that u are thinking of buying, then look at the sizes in her cloths/dresses...so what u'll have is something like this....36B for bra or size 10 in clothes....this may sound like idiot form but u would be surprised the amount of guy's don't know this....then once u got it, ask the store to fancy box wrap it for u. You could then either put a nice braclet inside it / earrings etc or some theatre tickets inside it.....i don't know how old she is or what she is into but something like mamma mia tickets or something, or put some cash in it....if ur gonna give her cash cos u don't know, then make sure it is given with something like the above....just giving the cash isn't romatic at all and any one can see there has been no effort been put into it. Then to finish the evening off, go for a meal. If she's clued up, she should be wearing the sexy stuff u bought......so when u get home u'll have the pleasure in looking at it..lol
hope this helps