Why does the Nurse take so long to tell Juliet about Romeo's response?

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.