How to achieve the effect in photos?

How can I achieve a tone and effect similar to this? I use a Nikon D5100 and a 18-55mm lens!

Take your camera out of auto mode and set it to over expose your images then you too can create images like this. Not exactly sure why you would want to, but it's simple enough to do!

It is NOT an effect, but a technique

The shot was done using back lighting. You should be able to see this by examining the photo in detail.

Take your cameras white balance out of "auto" and set the white balance to match the lighting.

The image is underexposed… Thats why the whites she is wearing are going grey… The background is overexposed, altogether i think its a weak image…

have a bright backlight that is stronger than the light hitting the subject…