Based on the rich and complex personality traits you've described, an appropriate name that starts with the letter "N" could be Narcissa Vexillon.
Narcissa captures her sophisticated charm and beauty, while also hinting at her sassy and mean edges. The name has a classic, strong quality to it, suggesting both independence and emotional depth.
Vexillon combines the idea of vexation and the concept of being a strong force, reflecting her reactive, abrasive, and complex nature. It also carries a certain elegance that complements her sophisticated demeanor but implies her unpredictability and potential for sadness or vengeance.
Together, Narcissa Vexillon embodies a layered individual with both elegance and an underlying intensity, resonating with the multifaceted personality traits you've outlined.