Why should Juliet be pardoned from the events leading up to her death? I have to prove that Juliet is not guilty. For example, one of my reasons...

It could certainly be argued that Juliet is not at fault for her eventual death. After all, she is only 13 years old and is deeply in love with an older man. She does act on impulse but she is steered toward her ultimate demise by the people around her. 

First, Romeo should have known better. He rushes into the relationship even though he lacks the maturity to make proper decisions. He probably should have consulted his parents before marrying Juliet. He also should have held his temper during Act III, Scene 1 when Mercutio is killed. He must have known that going after Tybalt, who was Juliet's cousin, could lead to tragedy. He also might have shown more patience when Balthasar delivers the message about Juliet's death. If he hadn't been so headstrong about committing suicide the Friar would have eventually gotten him the message about Juliet faking her death.

Second, Juliet's father changed his mind about Count Paris at a most inopportune moment. Previously, Lord Capulet told Paris to "win" Juliet's love. When Tybalt is killed Capulet backtracks on his earlier suggestions to Paris and promises his daughter to the Count. This presents a terrible dilemma for Juliet as she has to decide between betraying Romeo or defying her father. When she refuses to marry Paris, her father threatens to disown her, her mother spurns her and the Nurse advises her to forget Romeo and marry Paris. She has no one to turn to but Friar Lawrence.

Third, the Friar goes way too far in enabling Romeo and Juliet to act on their impetuous love affair. Although he thinks the marriage will end the feud between the Montagues and Capulets, which it does, it also costs the lives of  two young people he obviously loved. Even though he advises Romeo to "love moderately" and to take things slowly, he agrees with every whim on Romeo's mind. He even confesses to guilt in the double suicide. In Act V, Scene 3, he says,

I am the greatest, able to do least,
Yet most suspected, as the time and place
Doth make against me, of this direful murder.
And here I stand, both to impeach and purge
Myself condemnèd and myself excused.

Finally, the biggest culprit in the death of Juliet is the feud between the two families which has been going forever. It is stoked by the personalities who live at the time of Romeo and Juliet, specifically Tybalt and Mercutio. In the end, she was only doing what her heart told her to do. She didn't want to live without "her Romeo."