You can practically reach your girl friend's g-spot with your fingers. You just need to be patient and explore a bit to hit it right. Put your longest finger inside and explore. If you could feel a fleshy walnut inside the vaginal canal, that means you have spotted her g-spot.
It is a small lump that you can feel. Further, you can confirm through her quivering reaction. The moment you touch it, you can see her shiver in pleasure and you can see the kind of reaction that she would have never expressed, if you are touching her g-spot for the first time.