Come Lammas Eve at night shall she be fourteen.
Susan and she, God rest all Christian souls
Were of an age. (I.iii.)

Here the Nurse is counting down the days to Juliet’s birthday. The Nurse cares for Juliet like a parent. Juliet reminds her of her own daughter, Susan, who died young. Juliet therefore represents a surrogate daughter for the Nurse, and her link to the dead Susan foreshadows Juliet’s own premature death.

“Yea,” quoth he, “dost thou fall upon thy face?
Thou wilt fall backward when thou hast more wit,
Wilt thou not, Jule?” (I.iii.)

The Nurse fondly recounts a joke her husband once made about Juliet. The joke suggests that sex and harm are closely related, which in Juliet’s case will turn out to be true, since her first sexual relationship will result in complications leading to her death.

I think it best you married with the County.
O, he’s a lovely gentleman!
Romeo’s a dishclout to him. (III.v.)

One of the Nurse’s roles in Romeo and Juliet is to highlight the development of Juliet’s character. When Romeo is banished, the Nurse suggests that Juliet would be just as happy with Paris, because he’s better looking. Juliet disagrees, which shows that her passion for Romeo is no longer merely physical. Juliet’s disagreement also signals a break with her former trusted confidante. Indeed, Juliet does not tell the Nurse about her plan to fake her death.