Juliet comes to terms with Romeo’s killing of her cousin, because she loves him.
Many people call Romeo a villain, mostly relatives of Juliet, when he kills Tybalt. When she calls him a villain, it is usually in response to one of them.
When Juliet first learns that Romeo killed Tybalt, she is shocked and hurt. It is a natural response to learning that your husband killed your cousin. You do not want to lose either of them.
Beautiful tyrant! fiend angelical!
Dove-feather'd raven! wolvish-ravening lamb!
Despised substance of divinest show!(80)
Just opposite to what thou justly seem'st—
A damned saint, an honourable villain! (Act 3, Scene 2)
Juliet once again feels torn between family loyalty and her love for Romeo. She thought she had taken care of this internal conflict when she secretly married Romeo, determining that her love for him mattered more to her than his name. However, Tybalt targeted Romeo when he had the audacity to show his face at a Capulet ball. Capulet allowed Romeo to stay because he had a good reputation, but Tybalt was annoyed, and he felt his honor was impugned.
The conflict between Romeo and Tybalt had its basis in the feud between the families. It was a situation where Romeo just did not want to play along. This ironically, is what led to Tybalt’s death. Tybalt killed Mercuito, and Romeo felt he had to fight him.
Juliet knows that Romeo is a good man. This is what all of those contradictory statements are about. She is grieving. She loves him, despite what he did, and she knows Tybalt had a temper. She realizes that Romeo must have had a good reason for what he did, and she forgives him even though her family does not understand it.
Although her family is calling him a villain, Juliet does not play along.
Villain and he be many miles asunder.
God pardon him! I do, with all my heart;(85)
And yet no man like he doth grieve my heart. (Act 3, Scene 5)
Juliet is going to stand by her man. She does so to the end, actually. She no longer is willing to let him take responsibility for what he did, and lets Tybalt take the responsibility.
In some ways, Juliet has no choice. She has thrown her lot in with him. She could pretend she did not marry him, and marry Paris, but that would be dishonest and untrue. Juliet decides to remain faithful, and stick to Romeo.
In this story we have a situation where two young people are faced with a very tough spot. Romeo commits an act which determines both their futures, and Juliet has to decide if she is going to stay by him or not. They are young, and in love, and foolish but resolute. It is this foolish faith which is their doom.