1. A Box of Assorted Chocolates

A good way to surprise her on her birthday is with a box of assorted chocolates. Perhaps a heart shaped one. It has tiny little doses of sweetness. Each of the chocolate pieces is different. Each bite has a different flavor. The box has all the flavors that a chocolate lover could ask for. No girl can say no to chocolates and coming from the one she loves, there's no way she won't like it.
2. Kajal and Chocolate

It is said that the eyes are the way to the soul of the person. Then perhaps your girlfriend deserves to look as intense and passionate as her soul is, with a kajal. The kajal will bring out her true bold self. Bars of chocolate along with the gift will not let her energy flicker throughout the day.
3. Customized Mug

A mug is one of the gifts which may seem like a superficial gift to begin with, but if you customize it right, it is one of the best gifts a person can ever receive. Pick one of the best memories and get it printed on the mug. She will always have one of her happiest memories with her at all times and smile whenever her eyes would fall upon it.
Buying a birthday gift for Girlfriend is not as difficult as many say it is. She is your girlfriend and you love her. Close your eyes and ask your heart what would be a good gift for her. Whatever your heart says, go for it!