Sure, it is. Dork Diaries is in the realm of fiction. It weaves fictional tales that often involve the adventures and experiences of the main characters in a fictional setting.
It depends. Some parts of Dork Diaries can feel realistic, like the characters' emotions and school experiences. But there are also elements that might be a bit exaggerated for entertainment.
Well, Nikki has her crush on Brandon which is a big part of the story. Also, her battles with Mackenzie over popularity and status at school. And there are the times when Nikki tries to show her talents, like her art, in a school setting where she feels like an outsider.