What are the character traits of Nora?

On the face of it, it would appear that Nora is weak, unworldly, and submissive. In this, she is very much a product of her conventional upbringing. In those days, girls in respectable families were brought up to be seen and not heard. They were raised to be the next generation of loyal, subservient housewives who'd do whatever their husbands told them to do. Nora may have long since left her father's home, but her husband, Torvald, exerts the same kind of fatherly control over her, treating her like a small child who needs to be protected from a harsh, unforgiving world.
However, beneath the surface, the picture is more complex. For one thing, Nora's a good deal more worldly-wise than Torvald would ever have imagined. She certainly knows enough about the world of finance to forge her late father's signature to obtain a loan for Torvald's recuperation in Italy. Though she may have been treated like a child her whole life, Nora acts in this matter like an adult (albeit an unlawful one).
In addition to being more mature than anyone gives her credit for, Nora shows herself to be incredibly determined to do something once she's put her mind to it. As well as the incident with the forged signature, she shows impeccable drive and determination in leaving Torvald and her children, and the values they represent, behind. Whether or not one agrees with Nora's fateful slamming of the door, there can be no doubt that she's shown immense courage and resolve in taking this drastic step into an uncertain future.