How close to real do you want it?  I quickly took an overview of your render and noticed several things that would need to be addressed.  As you mentioned, DoF is a major component.  A sharp background in a portrait is very distracting and takes away from the main focus of the image.  

The lighting in the background shows either a setting or rising sun.  Usually, the color temperature is around 3000 - 4000 degrees Kelvin, a warm yellow-red to orange color emission.  You can see that on the outside of the cabin walls.  You may want that effect to spill over throughout the scene. 

On the model, the necklace is not casting any ambient occlusion shadows, it just looks like it's floating in midair.  Not very convincing in terms of realism.  There is a lack of skin texture detail, you can see that in her palm.  That might be a map problem or the primary light washing out the details.  

Your main light needs more adjustment, I gather that you are using it as a flash or portrait lamp to illuminate her face.  But I find it too strong because such a light would cast real shadows into your background.  Plus, there should be a light falloff into the distance, I don't see that effect in the trees behind her.  My recommendation would be to move the main light to either side of her face to cast some interesting shadows as opposed to the straight lighting you have now.  A backfill-colored light opposite the main light would separate her from the background better.  You would need to experiment with that.  

Soften the image, harsh details in a portrait do reveal imperfections.  

Question: is your background a static image or added props?