Aaah gladly. Disclaimer: women in the forum know best but I suggest thus... Don't focus on the gift alone, the bouquet of flowers must be deep red, and a creative florist could add some style.
I think a mushy card is allowed this once, not toooo loveeey (difficult for us guys), but with some heart. And it wouldn't hurt if the envelope was deep red too. Then if she's a chocolate person, a box can work; and if she loves wine, bottles are just above 500/- these days.
So you must get them delivered at the office. Yes office. And then you could go out in the evening to a place she likes, with some good music perhaps...
Then it wouldn't matter so much what you chose, as long as it's something she's mentioned in passing earlier and wrapped in red - women are always so communicative - you just need to have listened.