Another nice image, Javier, but I find this to be the weakest one of your recent postings. The main issues I have here are the distracting elements, followed by the crop. Let me cover those first and then look at a small issue with the skin tones.
1. In general, with a portrait like this, the subject should fill the frame, so that material above your model's head is not doing much for the overall use of space in the image. Crop that down.
2. The bright areas about 1/3 way up are quite distracting and removing them will strengthen the image. Some of this can be done by cropping from the left hand side (that space to the left of the tree) and the right (mostly fixed by cloning). I also cloned out that bright spot between the tree and the model.
The other issue is that large area of shoulder and back, which competes with your model's face. In a portrait, the face, especially the eyes are the most important part of the image. The back and shoulder are a touch lighter than the face, so it draws the viewer's attention, not the face. Burn that down to reduce the influence and you get a stronger image.
My final "trick" is to reduce the width of the image by around 5%, to slim down your model just a touch. People will not notice that "cheat" and the model will generally love you for slimming her down a bit.
The lens flare softens the image a bit too much for my taste, so I upped the mid-tone contrast a touch to counter the flare.