Capricious--an adjective often applied to many a female character. When Juliet first learns that Romeo is a Montague, for instance, she certainly senses danger,
Prodigious birth of love it is to me,
That I must love a loathed enemy.
And, she bemoans that Romeo's name is Montague in the balcony of the next act; further, she cautions Romeo against his impetuous declaration of passion that same night, warning that it is "too rash, too unadvised, too sudden," yet before he departs she declares her love--"I will not fail...I love thy company" and she marries Romeo the next day.
Later, in Act IV, she rushes to Friar Laurence in her quandary of how to avoid marriage to Paris because she is, unbeknowst to her parents, already married. When the priest gives her the vial to drink, she is conflicting about doing so out of fear of not awakening from it, yet she capriciously downs it, anyway. Then, in Act V when she discovers that Romeo has killed himself for her, she kisses Romeo's lips, hoping that some poison "yet doth hang on them" so she can die "with a restorative."
I would use the word trapped. I know it sounds like a strange word to describe emotions, but I think Juliet is trapped by her emotions. She is not able to think clearly. If she was, she would realize she does not need to marry Romeo instantly, and she would come up with a better solution than faking her death when her parents want her to marry Paris.
Fervent might be a word I'd use to describe Juliet's emotions. Her feelings are at a "rolling boil", so to speak. She is almost ill with passion. This is one way to see her character. The recklessness plans that she agrees to demonstrate just how fervent (and ardent) her feelings are.
I would use the word aggressive. Juliet is aggressive because she knows what she wants (Romeo) and will stop at nothing to insure he has him (in life or death). She is so determined to be with him that she chooses to end her own life if she has to live without him.
I think that Juliet is very tormented. Her love for Romeo clashes with her obedience for Lord Capulet. If she doesn't marry Paris then her father threatens to disown her, but on the other hand she can't betray Romeo who she is married to. This leaves her in a trapped position but her love for Romeo seems to override any other feelings as she is willing to kill herslef than marry another man and betray Romeo. This is also emphasized by the fact that she is able to forgive Romeo after he kills her cousin, Tybalt.