Women love to be romanced and that is the truth. I am with my wife for 19 years. I know her and what she likes. My advice is clean out the bath tub, fill it with nice hot/warm water and sprinkle rose petals in it. I would find some place that has cheap roses. Check the supermarket where they are cheaper. Make sure you light candles all the over place. You can have the dinner before just make sure that is candle lit as well. I do not know what your budget is but if you can give her a card with a bottle of perfume, the dinner, the tub and finish with a massage you are sure to get your gift by the end of the nite.
You can spend well under $100 on this if you do it right. Good luck.