Here are a few different gift ideas that may work for your girlfriend based on her hobbies and interests:
If she wears earrings, these little studs that are designed to look like balls of yarn with knitting needles stuck through them are adorable. They are handmade by Max Alexander, an avid knitter who knits beautiful moths and butterflies. The blue ones that I posted to the left are really pretty since they have a metallic thread running through them. If you don't like them, though, they come in a bunch of different colors as well.
She also makes some other knitting-inspired jewelry including necklaces and bracelets if your girlfriend doesn't wear earrings. Right now, the price on the studs is $14,95 a pair, which isn't bad for handmade earrings. You can check out some of the other colors or jewelry styles here:
You could get her a subscription to Watercolor Artist magazine. One of my favorite things about giving (and getting) magazine subscriptions as gifts is that they continue to show up all year long. Although I've never actually looked through a copy of this magazine myself, from what I understand it has a lot of tutorials and introductions to interesting techniques. It's also supposed to have a lot of beautiful paintings by watercolor artists throughout the world. I would imagine it would be fun and inspirational for someone who was into painting.
The only downside is that there are only six issues a year, which means it would only show up every other month. A year's subscription on Amazon is $21.67 right now, which means you could also afford to get some paints, brushes or paper to go along with it if you wanted.
Here's a link where you can subscribe for her:
Although it's a little bit hard to see from the picture, the camera lens to the left is actually an insulated travel mug. The body of the mug is designed to look just like a lens. I think it would make a really cute gift for someone who loved photography -- especially if they also enjoy drinking coffee, tea or other hot beverages on the go.
It only costs about $20.00 as well, which means you could always get here something like a selfie stick or a small tripod to go along with it. It holds 11 oz. and is lined with stainless steel to keep drinks warm for a long time. You can grab one here:
Hopefully one of these ideas will work out for you!