At first, Juliet copes with the news that Romeo killed Tybalt by realizing that she should not speak poorly of her husband, no matter what. When Juliet's nurse begins to say that there is no honesty in men and that Romeo is shameful, Juliet responds by declaring "Blister'd be thy tongue for such a wish! he was not born to shame." In fact, Juliet begins to reason in the same manner that Friar Laurence does: She should rejoice that Romeo killed Tybalt, who was about to kill Romeo.
But then she begins to cope quite poorly. She begins to react in the same way that Romeo reacts to the news that he has been banished. Juliet also feels that being banished is as bad as being killed; or as bad as having her entire family killed, as she alludes to in the line: "'Romeo is banished,' to speak that word, is father, mother, Tybalt, Romeo, Juliet, all slain, all dead."
Finally, just like Romeo, Juliet deals with Romeo's banishment by also declaring to commit suicide. Juliet takes up cords that Romeo must have meant to use to climb up into her room and declares:
Poor ropes, you are beguiled, both you and I; for Romeo is exiled: He made for you a highway to my bed; but I, a maid, die maiden-widowed. Come, cords, come, nurse; I'll to my wedding-bed; and death, not Romeo, take my maidenhead!
Hence, at first Juliet copes well with the news, refusing to think badly of her husband, but then crumbles at the thought of him being exiled.