Zana Marjanovic was up until recently, a largely unknown Bosnian actor. Not any more. Angelina Jolie has recently chosen her to play one of the leads in her directorial debut about a Serbian man and a Bosnian woman who fall in love on the eve of the Bosnian War. Zana's smile is sincere - with a relaxed forehead, eyes partially closed, cheeks raised & bunched-up, her upper lip raised exposing the top teeth, while the lower teeth are covered by the bottom lip - are all consistent with sincerity.
Because she has recently come into the acting world's limelight, it is natural that she would be somewhat less than 100% confident. We see evidence of this in her arm-crossing - which is a signal of defensiveness, a desire not to engage, or a closed-off emotional mindset. I have no doubt that her smile is sincere and her joy at landing this life-changing role is very real. But going from the farm team to the major leagues is intimidating and she's experiencing emotional dissonance. She's a professional actor, and better than most at hiding her emotions - but just like the rest of us, the truth always leaks out.