Cute model, although her expression looks pained and unnatural. The reflection of light in her eyes is distracting to me. The hair fly-aways also are distracting, I would prefer either a more windblown look or to edit them out.
This is kind of a strange shot for me. On one hand, she's obviously a very attractive girl, but in this shot it's hard to tell if she's happy or on the verge of crying. I guess it could be that she's squiting in the light or something... just strikes me as an odd expression :)
The lighting is working well here. Its making her face seem very flat, as it is direct front lighting. Next time, have her turn her head to be at a 45 degree angle with the sun, this will give the portrait more dramatic lighting, and give an overall better effect. The focus seems a bit soft as well around the eyes, which is where critical focus should be obtained in a portrait.
ow, you made her look into the light. She's in pain and you can see it on her face. I know you wanted good lighting, but try having her look in a different direction next time. People with light-colored eyes have trouble on bright days because their eyes reflect more light than absorb (unlike brown eyes). Just a tip.