girl on a mountain

You have a great location with this shot.  You have a difficult exposure parameter to address, in this case, you have under exposed the young lady and over exposed the sky.

This is really a shot that you need some flash to bring out the person while you expose for a beautiful background and sky (which will give you more color saturation).  I don't know how high the rocks to the camera's left go, but I would have been tempted to use those rocks as my light source and aim my flash to bounce off of the them to expose your model while capturing/exposing for the natural light in the background.  By doing this, you would have achieved more depth to the photo as your model would have popped more against the background.

The current picture is fairly flat due to the lighting.  Check out this link for some ideas on how to use flash without anybody knowing you used flash.  http://neilvn.com/tangents/flash-photography-techniques/

In a case like this, using fill flash (which I try to bounce whenever possible), I would also bracket your exposure and/or flash.  It is better to have 5 not perfectly exposed shot and 1 shot with perfect exposure than it is to have 10 shots with non perfectly exposed.  Often times, it takes until we get back home until we realize the exposure could have been better.

You will hear lots of self proclaimed "purists" espouse that using a flash is wrong.  And if done poorly, it is.  But if they could learn to use it correctly, which is not easy, they would change their minds quickly.  Not all shots are better without flash than with proper executed flash (and I am not talking about a truck load of equipment, wireless slaves, etc. . . just a true on-camera, hot-shoe mounted flash).

Composition I will leave to others to comment on.

FYI, I am no expert and probably shouldn't even be commenting.  I commend your courage to seek critique, feedback and gain knowledge.  

Thank you, Chris.  

No comments are unwanted.  So, thank you for yours.  I wasn't making this shot as a staged one.  We were just hiking and I was using a camera.   This shot was as is.   I slightly darkened the sky in lightroom, just to make the clouds stand out - they were blending with the background and shalowing the background.  And yes, I am known to make photos darker - somehow they appeal better to me. ... Working on that flaw.

The catchlights in the glasses tell me you were using a bit of on camera flash fill--but it needed to be a bit stronger.  This is a backlighted scene so the light on the woman's face in wrap-around skylight, a soft omni-directional light that will not create a highlight/ shadow ratio on the face the way a studio portrait would.  Don't spend time trying to bounce flash outdoors because it does not work.  The charm of this composition is the outdoors and nature with a nice balance and use of space.  I increased the contrast overall and raised the levels in photoshop.  I selected the woman and the rock she is sitting on and adjusted the levels and curves.  I hope this is helpful.  Good luck.