What permission ("leave") does Juliet have in Romeo and Juliet and why is it important to the action in Act Two, Scene 5?

Act II scene 5 is vital to the plot of this excellent and
famous Shakesperian tragedy in a number of ways. First of all we see Juliet, awaiting
her Nurse, who has gone to meet Romeo in her stead to see what message he wants to give
to her. We meet Juliet eagerly and anxiously awaiting the Nurse, although she is not
back when she has said she would be. Juliet has obvioiusly been given leave to wait for
her and therefore get the response that she has been hoping for from her lover, although
the Nurse takes a very long time in giving it. Finally, however, she
says:

Then hie
you hence to Friar Laurence's cell;

There stays a husband
to make you a wife.

Thus this
scene is crucial to the overall play because in it, Juliet receives the news that she is
to be secretly married to Romeo and achieve her true heart's desire. Of course, this
will have radical ramifications when Romeo kills Tybalt.