Inspired by maternal feelings and a servant's deep loyalty, the nurse agrees to help Juliet marry Romeo.
When the nurse meets Romeo in act 2, scene 4, she tries to determine whether Romeo's love for Juliet is genuine or whether he is merely infatuated with the beautiful young lady.
But first let me tell ye, if ye should lead her into a fool’s paradise, as they say, it were a very gross kind of behavior, as they say. For the gentlewoman is young, and therefore, if you should deal double with her, truly it were an ill thing to be offered to any gentlewoman, and very weak dealing. (act 2 scene 4)
Here, the nurse's words demonstrate her protectiveness towards Juliet. The nurse's behavior indicates an abiding affection for Juliet. It is the nurse who acts as a messenger for the lovers. Her discretion and resourcefulness makes it possible for Friar Lawrence to marry Romeo and Juliet in secret.
In act 3, scene 5, the nurse warns Juliet that her mother is coming to her bedroom. At the warning, Juliet has to pull herself away from Romeo. Later, when Juliet's father announces that she is to marry Paris, it is the nurse who speaks up on Juliet's behalf. For her solicitude, the nurse is berated by Lord Capulet. Here, it can be seen that the nurse is ready to jeopardize her position in the Capulet household for Juliet's sake.
Yet, the nurse is also a pragmatic woman. She realizes that Juliet's future and survival depends upon her honoring her parents' wishes. So, she advises Juliet to forget Romeo and to accept Paris as a husband.
The nurse's advice seems to contradict her earlier support for Juliet. However, her ability to be both loyal and pragmatic is evident in the advice she gives her young charge. The nurse's chief priority in life is to protect Juliet. The nurse believes that, by marrying Paris, Juliet will ensure her survival in the deeply patriarchal society they live in.