I always check the catch lights in the eyes first. It appears to be a fairly small-sized light on the left at eye level. But the shadows are so open that I wonder if there might be a big white wall (reflector) behind the photographer or a fair amount of post processing.
The eyes say its sill flash camera left, about the same height as the camera.
As for the shot, I don't care for it. It does nothing for me and I find a LOT I don't like about it (composition, crop, clippings, background, lighting, etc.).
I always check the catch lights in the eyes first. It appears to be a fairly small-sized light on the left at eye level. But the shadows are so open that I wonder if there might be a big white wall (reflector) behind the photographer or a fair amount of post processing.
I'm going to say camera left about 45 degrees up. If you look at her left nostril you will see a highlight, also her index finger holding the unbrella has a round dot on it which would be a light source reflection.
Her eyes show two catchlight as well, one from the bottom left too. I'm guess a reflector down there as well, just not as powerful as the sun and the top left light.
My guess would be that there is a silver reflector being held to the left side of the camera position. It could also possibly be a flash. The fill is likely what is causing the catch light - judging by the sharp shadow around her neck the sun is too high to be reflected in her eyes.
My guess is it's got to be an off camera strobe that's almost equal to the ambient light. You can see shadows going both ways, especially off her nose and mouth and then the one from her chin on her neck.