Watercolor study of young woman

Here we are!

This is my first work. It is a study taken from a very little photo of my girlfriend, Sara. I changed the font of the light (the quality of the source photo is awful), and this is my problem: can you help me to look for the matters in this sketch?

Don't be comprehensive. I just want the holy truth. I want to improve myself and learn from all of you. If anyone want, I'll send the source photo and the chaircoal sketch.

Consider that this is a study for a future oil underpainting.

Thanks to All,
Alessandro