Why is Juliet presented as a determined character?

Juliet has to be a determined character to get what she wants, which is Romeo. So many barriers have been put in her way by her family and society that the chances of Juliet spending the rest of her life with the man of her dreams are remote, to say the least. Most young women in Juliet's situation would just give up; they'd yield to their parents' wishes and do what society expects of them—albeit reluctantly. But Juliet does not give in. Her love for Romeo is so all-consuming that she's prepared to defy her parents and the prevailing social conventions and do whatever it takes to be with him.
As a young girl in an aristocratic family, Juliet is expected to be seen and not heard. This is a society in which marriages between noble families are regarded as strategic political alliances, not love matches. Marriages are arranged, and the wishes of the respective partners are of no concern. The odds, then, are heavily stacked against Juliet. She must be determined, she must show spirit, and, more than anything else, she must take risks, even with her own life, if she's to be with the man she loves.