How old a woman are we talking here? I think you'll find radical variation depending on what generation the person belongs to. If she's over 50, I think she'll generally just be glad someone is still paying attention to her, but also that generation of women didn't grow up under this current poisonous "whoever shows the least interest wins" culture. She will find flowers to be a touching gesture.
If she's younger than say 27, I'd say flowers, at any time and for any reason, are only going to lose you points, or more probably the whole ballgame. Any gift at all, for any reason, will smack of desperation, and you'll have instantly lost the upper hand, and she will loathe you without knowing exactly why.
From 28-49 it's basically a toss-up. Since flowers are literally the least-imaginative, most clichéd thing you could do for a woman, it will depend on how boring a person she is overall. Does she work in an office? Does she regularly watch television? Does the music she listens to appear on the "billboard top 100" charts? Has she, in the last six months, eaten at a theme restaurant similar to TGI Friday's or PF Chang's? If she possesses a passport, does her passport contain fewer than three entry stamps to non-US nations? If you answered yes to any of those, she'll probably dig getting flowers, and oddly enough, doing anything MORE imaginative and less cliché than flowers would likely hurt you. She'll think you're a dangerous oddball for colouring outside the lines.