Good things to say to your girlfriend, and more reading
The most commonly used one and another good source of inspiration is food. You can choose from fruits, like strawberry or you can choose from sweets, such as cupcake. Your girlfriend will love that you see her as sweet and cute as those sweets and fruits. But make sure not to call her anything that is connected to heavy meal, like pork chop. She will think that you see her as fat and she will surely not see that as cute.