Hi Mikie,
A successful portrait, or any photograph, should have the subject be predominant within the frame, i.e. the viewer should immediately see what the main subject is.
In the first photo, the subject is not predominant, the haystack in front is bigger and also very sharp, the tree behind is bigger and the composition has placed her completely to the left with a large open field taking up most of the photograph. My question is therefore, is this a portrait or a landscape that happens to have someone in it? If I'm asking the question, it means the photo is not providing the answer.
In the second photograph, the subject is the main point, however the tree just isn't adding to the composition, it's just too damn big. It's probably a good idea to reposition the subject away from the very centre as well, with the subject in the centre and the tree to the left, this image is very unbalanced as there is nothing to the right to counterbalance it. The image is also too dark, at least by one stop.
Now I have a suggestion. As you want to learn, take what I have said above, study the third photo and see if you can determine what works and what doesn't. Once you've done this reshoot it accordingly. This will develop your internal critique and help you compose successfully for future shoots.
Hope this helps a bit, any other questions and the rest let me know
Steve