Your labia minora are very stretchy and you can pull them regularly to make them longer. Pulling and stretching the labia is also a pleasurable activity and many girls just do it for the erotic fun of it.
It is wise not to stretch them always at the same spot. Try to pull your labia from the front, bottom and back so they can lengthen evenly. The girl in the picture above for instance could also grab her labia closer towards her anus and pull on that part. It will avoid the inner labia to become thin and pointy.