IDad is certainly right that without the original image we're just guessing. First thing with this image is it is professionally done, whether outside or in (iDad would know better than I). It is important to start with a good photo to really get the whole effect. But you can still simulate the result for just about any photo.
But you can see, this starts with a woman and an environment that is not full of saturated color. No red dress. Also, I think there may be a selective enhancement of color on the rocking horse and some punches of color on her lips and cheek.
I gave it a quick shot with the following picture. By no means is it a perfect reproduction of the model above. Of course.
I duplicated the original layer and desaturated it, set it to screen with a lowered opacity of ~65. Then I made another desaturated layer and set it to multiply at about 30% opacity. I also went back to the color layer and added a sepia photo filter. (to be found under layer adjustments, not filters)
Reproducing this kind of effect without a tutorial from the photographer/post-production person or from someone who regularly does this kind of effect, means that you get to experiment. The steps I took might not work for a photo you have in mind, but will put you on the right track.
Of course, this being Photoshop, there are more ways than one to go about almost anything. I was going to see what might be achieved with the HDR toning effect. So . . . :mrgreen:
original photo by sunniede82, deviantarts.com
altered photo