She is saying here that she knows Juliet's exact age, which shows she has become more of a mother to Juliet than lady Capulet.
You can see Juliet feels at ease talking to the nurse by the way she responds to her and confides in her, she talks more formally to her mother, like calling her madam.
Lady Capulet tells the nurse that Juliet is going to get married to Paris as she's fourteen and old enough now, but the nurse tells Lady Capulet she doesn’t agree and Juliet will not marry him. The nurse's impact on the audience is that she knows Juliet a lot more than Juliet's mother. The Nurse is very open with her opinions, advice, and feelings with Juliet.
When Juliet meets Romeo for the first time the nurse is the one to tell them both the identity and forbidden namesake of the other, you can see Juliet trusts the nurse as she tells her the secret plan to marry Romeo
The nurse holds Juliet's happiness so high that she betrays her employer and arranges Juliet's marriage and honeymoon night with Romeo, by this you can see the nurse really cares for Juliet as she is willing to loose her job and possibly her life to see Juliet happy.
In Act 2, scene 5, Juliet awaits the Nurse's return with news of her marriage to Romeo. In this scene Juliet proves very fond of the Nurse by using sweet names for her;
'O honey Nurse.' (Act 2, scene 5, L18)
The Nurse delays giving Juliet information about the marriage, which creates tension for the audience. This also makes the play much more interesting, creating suspense and drama. It takes the Nurse from her entrance on line 18 until line 68 to tell Juliet about Romeo awaiting her at Friar Lawrence's cell.
The nurse acts as a go between for Romeo and Juliet giving Juliet secret messages from Romeo about the wedding plans, without her and Friar Laurence they wouldn’t be able to get married.
After Romeo is banished for killing Tybalt the nurse is the one who tells Juliet but Juliet thinks it is Romeo who is dead, when she finds out its Tybalt she is quite relieved. This creates confusion, yet excitement and suspense to the play.
The Nurse begins to turn on Romeo and compares him unfavourably to Paris, by calling him names. This contradicts everything she ever said about him;
‘Romeo's a dishclout to him.’ (Act 3, scene 5, L219)
Her role changes as she suggests that Juliet should forget about Romeo and marry Paris, she loses Juliet's trust and confidence. Juliet decides to seek the help of Friar Laurence, thereafter she no longer involves the Nurse in her secret plans as she feels betrayed by her.
Juliet has now taken the potion which will make her appear dead, so she doesn’t have to marry Paris. The nurse is the first person to find Juliet dead, she enters the room and seems excited that Juliet is getting married and she is the one who is going to help her get dressed, she thinks Juliet is sleeping and says;
‘Sleep for a week, for the next night I warrant the county Paris hath set up his rest that you shall rest but little.’ (Act 4, scene 5, L5).
This shows her sexual humour as she is saying that she should have a good sleep as she will be up all night with Paris. The nurse realises Juliet is dead and is finally for the first time in the play lost for words and silent.
The nurse is an important character in the play because Shakespeare uses her to move the plots forward in a dramatic way. She is like a messenger informing Romeo and Juliet of the news and keeps the story going. Shakespeare also uses her to bring humour to the play which contrasts with the tragedy which happens at the end. Without the nurse the play wouldn’t have been able to develop as well as it did.
Bibliography
Websites
Books
Richard Parsons (2002) GCSE Shakespeare, Romeo and Juliet, Coordination Group Publications.
William Shakespeare (1998) The oxford Shakespeare, the complete works. Editor Stanley Wells, Oxford University press.