The Nurse's delay in this early scene seems to function in two ways. First, this shows the playful relationship the Nurse and Juliet share. These two have been companions for all of Juliet's life, and we sense that Lady Capulet scarcely knows her child. She was unwilling to be alone with Juliet when she told her that the family wanted her to marry Paris. In that scene as well, we see the talkative nature of the Nurse and how she likes to tease Juliet. As the Nurse helps Juliet embark on her first love affair, her fondness for both Juliet and love spill out. She wants to lengthen the news to tease Juliet and to make the good news even more appreciated. She also is able to get a brief back rub out of the anxious Juliet. In this scene, we are charmed by Juliet's warmth and impatience and humor.
The second reason is more formal. This play tends to have multiple double scenes. We have two fight scenes—one comic and one serious; two balcony scenes; two Juliet death scenes, and such. We also find two delay scenes that look very much alike. Later in the play, the Nurse will return with news that Romeo has killed Tybalt. Again, the Nurse is slow to give Juliet the news she awaits. In this scene, Juliet goes through multiple stages of grief and resolution and in doing so shows her sophistication as well as the rationale for her doing what she chooses to do. In these short minutes on stage, Juliet grows up more than most people do in a decade.
As she does in Act I, Scene 3 (when she carries on about Juliet's age), the Nurse provides a good deal of light hearted comedy in Act II, Scene 5 when she playfully evades Juliet's anxious requests for news from Romeo. The Nurse claims that she needs a few moments to compose herself, and she has been through a bit of an ordeal as she was rudely accosted by Mercutio in the street before she was able to speak with Romeo in the previous scene. She complains to Juliet, "I am aweary. Give me leave awhile./Fie, how my bones ache! What a jaunt have I!" The Nurse obviously senses Juliet's restlessness and exploits it, probably for her own pleasure. Juliet and the Nurse are, in many ways, very close friends and share each other's secrets. It is often typical of friends to tease each other and this is precisely what the Nurse is doing as she knows full well that Juliet is bursting at the seams to learn Romeo's plans. Eventually, the Nurse reveals that Juliet should come to Friar's Laurence cell where she will be married to Romeo.