Selecting an appropriate birthday gift for your Sikh girlfriend involves considering her individual preferences and beliefs. It's important to be respectful of her cultural and religious background. You might consider a gift that aligns with her interests or a piece of jewelry with a meaningful Sikh symbol, such as the Khanda. Alternatively, planning a surprise birthday celebration that includes traditional Sikh elements, like delicious food and music, can be a thoughtful way to honor her culture while celebrating her special day.