I would like to suggest that despite all the things you can buy off the shelf, there really isn't anything that speaks more sincerity and love that a personal DIY-ed (Do-It-Yourself) present. This can be in the form of composing a sweet personal poem for your loved one, or carving out her name with scented candles.
Let your creative juices flow, anyone can buy anything off the shelf, but to really move your girlfriend, show her that she's worth more than just picking an item off the shelf. Many people says it's the effort that counts; well, show her how much effort you'll be putting in by making her a present. A trip down to IKEA would fill your mind with ideas on what kind of DIY presents you can make for your girlfriend.
A few ideas : Photo collage, poem, carved scented candles, your own love storybook if you have the time.