Do you have any mutual friends? Try to arrange for a small group outing where you can speak w/her in a non-pressure environment. Get her attention and then drop an easy apology "BTW, remember when...? Sorry, i was really ____ & I wanted to let you know that I think _______" etc. See what evolves.

You could always just try asking her out for coffee or something direct. In person is always best. You can read her body language and shows you've got some moxie. The flowers seem a little overdone, given the timespan, unless you really did something stupid/mean to her. Depends on her maturity. Is she dating anyone? I have other ideas, but so much depends on her personality...

DON'T immediately tell her you've been thinking of her all this time. There's nothing wrong w/it, of course, but many people would be weirded out. Especially since there isn't much history b/t you...?

If all else fails, try this: http://www.sharpman.com/Article.asp?ArticleID=128

Hope this helps.