ManlyB has said it all. Other thoughts to consider might be: How did you meet her? Have you participated in any online? Has she lost anything which she would be touched if you replaced? Is she starting a new job? Moving? Growing her hair out? Does she like spas?
Without knowing more about her life and interests, none of us can likely help you with gift ideas.
Case in point: If you bought me a diamond, I'd immediately pawn it and make a donation to an African charity. If you bought me a cookbook, and it pertained to something going on in my life (such as my recent trip to Puerto Rico, my impending trip to Japan, my current life in Boston, my upcoming move to Miami, or local foods from your area) you'd be my hero. But then, I'm a pastry chef.
I have always wanted a man to send me a balloon bouquet. Maybe some day, someone will. My man doesn't know, and unless it comes up, I ain't telling! If he ever sends me a whole gaggle of balloons for no reason, I will just melt.
He's drawn me a picture of myself as an anthropomorphic cat. Best. Gift. Ever. But then, when we were just friends, we spent time at a role-playing site, and my character was myself as a cat.
Do you see what we're saying about how your gift must be very personal if it is to leave a big impact?