Juliet has been an obedient girl throughout her life. She has lived under her father's roof and does as she is told like she's supposed to. However, she takes her first stand for independence in Act III, Scene V, when she defies her father by refusing to marry Paris. Her father disowns her for her action, yet she is content to break ties with her parents if that's what it takes to be with her Romeo.
Juliet's act of courage is also prompted by her desire to be with Romeo. After her father's tirade mentioned above, she seeks out Friar Lawrence for advice about what to do next. He comes up with an elaborate plan to fake her death in order to avoid marrying Paris and to be with Romeo instead. It takes great courage for her to swallow the potion the Friar offers her because she doesn't know if it will work, but her will to be with Romeo outweighs her fears.
Romeo and Juliet are passionate with each other many times. The example that stands out is when she finds out Romeo killed her cousin Tybalt, she ultimately forgives Romeo knowing in her heart that he had no other choice. The way she chastizes the Nurse for speaking poorly of Romeo and the deepness of the depression she falls into when she learns Romeo has been banned from Verona, shows the high amount of passion for which she loves him.