I think that Zlata's character is no different than many fifth grade children.  She speaks of vacations and the same life that many children experience with school and their own world.  Where her character takes a sharp turn that helps to form the crux of the narrative revealed through the diary is in how Zlata responds to the war.  She represents a characterization that undergoes maturation and a growth after being placed in a situation that would test the character of many adults.  In recognizing the reality of war that has descended upon her, there are immediate fears for her family and loved ones.  There is also the challenge of how to maintain safety, and taking care of herself while living in constant fear.  It is here where the diary becomes of the utmost in importance for Zlata, an outlet for her to relate her concerns and the fears that grip her.  In this, one sees how she deals with the challenges of war.  I tend to think that Zlata's character at the start of the narrative is reflective of how a life instantly changes when war becomes part of daily existence.  In Zlata's case, war becomes the demarcation point between the time when she was a regular fifth grader and when she became older than her years because the condition of war prompted her to have to adapt to a time where innocence is gone and grim reality settles into her psyche.